Where abouts in a west coast zone 8 are you located? Phormiums are not uncommon plants pretty much anywhere along the west coast and I'd have a hard time imagining too many of the local larger retail nurseries not carrying a good selection......you can even find them at my local HD!! One caveat, however :-) I'd suggest that rather than looking for very specific cultivars - which may not be all that readily available - take advantage of whatever cultivars offered that fit your requirements. Phormiums are really only borderline hardy in zone 8 and if you live in the PNW zone 8 with our routinely wet winters coupled with a good arctic blast or two, it is unusual to find phormiums surviving more than a couple of seasons. In fact, a good many PNW nurseries now treat them as more or less seasonal plants. It would be a shame to invest too much $$ into a lot of different and hard to find phormiums to not have them survive for very long. FWIW, I have never seen phormiums offered bare root. Not a common sales method for an evergreen plant :-)

Phormium tenax is usually naturally found in lowland and swampy areas perching on hummocks. Has very stiff and upright leaves to about 10', though some of the purple cultivars are definitely lax. Dark red flowers and seed pods. Will easily take moderate frosts down to about -8C. Usually grows out in the open, in full Kiwi sun. (High UV.) Summer temps usually around 20-30C. Phormium cookianum/colensoi is often found on hillsides up to about 1200m and in well-drained gullies. It has more floppy leaves, yellow flowers and brown twisted seed pods. Easily takes frosts and some snowfall, though not lasting. More of a bush-edge plant but also ok with being open, though it may not grow as tall. Both tolerate droughty spells. And frequent winter rains. Both have a very tough covering on the leaves, though they will fray if they suffer a lot of wind. Hardy by the sea. Possible over-wintering - cheat and remove a young fan from the rhizome. Trim it as you would a bearded iris - with the young growing tip being in the middle and the longest. Plant up in a gritty but moisture-holding brew so the roots will develop well. (If your summers are brutal - pot them on to something more moisture retentive.) That's insurance against disaster. If there aren't many pots then the inground proposal seems good - plus traditional hay bales around the edges and a thick cover of ag plastic, bubble wrap, fleece, old blankets - whatever is suitable for your area. When you bring them back for spring-summer harden off carefully so that leaf 'wax' can rebuild because that is what provides a lot of the hardiness. Mealy bugs. I would suspect deep droughting in the container or the lack of water-holding in the mix. Good drainage, yes, but not the sort of miserable mix that pretends to be wet on top while holding the lower reaches from rewetting. A possible solution (for some) may be the addition of pumice pieces of about 5mm to the mix. And repotting every one to two years, or adding a good organic mulch. They have extensive root systems and will quite quickly fill a container.

Don't recall seeing any Phormium locally, but are available from Forest Farms and other on-line/mail retail nurseries. Nolina texana can look very nice in containers. Though not sure it will thrive in full sun in north Texas. Also will eventually become too broad to grow anything around it's base in a 24" pot. Other options that come to mind are nassella tenuissima (Mexican feather grass) and muhlenbergia capillaris (gulf mulhy) which should both do okay in full sun here. Here is a link that might be useful: Phormium at Forest Farms

It is either P. cookianum (now known as P. colensoi) or a hybrid, as P. tenax has rigidly upright leaves. As to which cultivar (if any), I have no idea :-) There is nothing very distinguishing about this one, while the brightly colored or variegated ones are easier to identify.