For my corner posts I used hedge posts 1 foot or so in diameter and used a sharpy shovel to get them about 4 feet in the ground on a 20' run. The grapes get so heavy they break / bend woven wire fencing I used and I frequently mend it back together. I would cut another peace of hedge that looks like a Y to hold the posts in place on each end buried sideways at an angle or use a steel braded cable with a stake driven in the ground or both. Like you I used T posts in the middle and a hedge post in the middle as well. Believe it or not the weight depends on the type of grapes with seedless concord being my heaviest variety. I made a mistake and planted them 6' apart instead of 8' as recommended and they grow thick fast because of that. Seedless concord are a very aggressive variety in Kansas and they put out lots of foliage. They grow so long in some years the ends start to root where they touch the ground. Red canadice for example have nice small canes and are not overly thick or difficult to support. I planted them 6' apart and they never grow any larger than that for the most part. I aggressively trim my grapes every year. Because we do not have lots of water the idea was I trim the grapes to 6' instead of 8' so they don't have as much plant needing water. I've killed grapes back to the ground here by letting them grow out to long. I still plant new varieties close together but I will allow 8' for seedless concord next time.

you would need to attach a batten - lengths of wood, at least 50mm thick, to the wood fence using normal woodscrews attached to the posts which hold the panels in place. Then fix a trellis to the battens as the width of the battens allows for some ventilation - you are right inasmuch as a rose, or any other climber, does better if not totally flat against a solid wall. Sinking a wood post against the concrete fence would look the same as if you had attached it rather than having it free standing - essentially, posts are supports for trellis, wires or panels. A tepee is wider and will cover more of the wall than a pillar and once the rose has reached the top of the fence, you can train it horizontally along or even cascading over to the other side. You will need a posthole shovel, sand and cement and a drill in order to make a free standing trellis support. Conversely, you will only need to sink 4 lengths of rebar, 60cm into the ground to make a pillar. The choice is yours. Both ways will work fine.

Re: growth rates - you hear it applied to all sorts of other plants, but this saying truly applies to clematis: the first year they sleep, the second year they creep and the third year they leap. It takes time for a clematis vine to become fully established and you will most often get your best results both in vigor of growth and production of flowers from year 3 onward. In the Seattle area, there are few locations where one can't grow clematis. Just avoid areas that receive too much shade - light shade is fine for many types. Also areas that may receive too much root competition from other established trees and shrubs. And understanding the reason behind the coda of shading the roots expands the possibilities - it's not so much as the roots requiring shade as it is not allowing the soil around them to dry out. And shady soil generally holds moisture better than open, sunny soil. But if you water appropriately in summer and mulch the root zone well, you can plant clematis in a full on, full sun southern position without fear. A couple of other notes on new clematis: prepare a generous planting hole, well-enriched with organic amendments. Plant the vine 3-4 inches below the level it was in the container, generally up to the first set of leaf buds. And prune all types of clematis hard after the first season in the ground. Both the deep planting and the hard pruning will encourage the development of a healthy root system and the production of additional basal shoots, increasing resistance to wilt problems. As to trellis or support size, research the expected size of the clem of your choice and select a trellis or support accordingly. And even this is not a hard and fast rule but merely a guideline. I've grown larger types of clematis on rather short supports - they just grow to the top, then cascade over, making a waterfall effect that is pretty stunning come flowering time.

I use electrical conduit from HD - wait til they go on sale in spring as the 10' lengths for 1/2 in are $3-something now, half that when on sale. Cu is way too expensive unless you want an architectural element - if for function only should be conduit. Galvanized is OK but more expensive. You'll need a pipe bender - borrow one from someone. I secure my conduit to the ground two ways: 3/8 x 3' rebar 2' in the ground or 3/4 sch40 PVC 1' in the ground (windy here). Rebar is more flexible location-wise as PVC is more effort to install so you don't want to dig up and move it. I think PVC is more secure. You'll need slip-on connectors - I use the ones with two screws as the screws help keep things like netting and string from sliding around. 6' tall for determinate tomatoes is OK, indeterminate will overtop but unless you are 5'8" or over, more than 6' tall trellises you'll need a step stool, which is problematic in soil for compaction and stability. My overtopping toms last year meant I tied the vine to the top and kept it horizontal- not ideal but I get some production. Real issue with how tall trellises are is fall frost danger and what do you do to them to protect from frost and your height of trellis determines your strategy. I'm 6'2" so mine are at 6'6" and garden is against house, so I secure 6 mil plastic to brick and then to ground. If you take off and lay on ground and cover toms, then you have to put them back up again and where will you put stepstool to do that if the toms are on the ground? Peas OK on mine, pole beans can go higher but just tell them where to go, my melons are on 3/4" conduit because I overengineer everything, squash OK also, heavy producers may end up on 3/4 this year. Twine is cheapest and toms easily supported by it, but I double twine. Nylon parachute cord is better, but costlier and may make it 3 years before breaking - but your configuration of string is going to change every year anyways. Squash and melons should have heavier string than cheap twine. Peas like netting, my cukes don't care, squash is easier with netting, not sure which is easier for melons but I use string for them & it works out. HTH. Dan