Once it's killed with Roundup I would think dead is dead. After the roundup to make sure ALL is dead, you might want to water it again to see if any green. I used a 2 prong hoe to dig it up, but only had about 100 sq feet to do. It helped to water the area the night before.

I think your new plants will do better if all the sod is gone.
Some cities are offering rebates to replace lawn, but they must approve the plans...something to check into.

Here is a link that might be useful: 2 prong hoe

The problem with Round-up is that (1) it doesn't get the weed seeds in the soil and (2) you still have to somehow dig up dead grass once the grass is dead.

I always suggest getting up the sod with a rented sod cutter (do it yourself). Roll it up and haul it away. Yep, it's hard work but it's the best in the long run, especially if you don't want to continually hack away at weeds.

Then start watering the plot to bring up weed seeds and any grass pieces you've missed. Water every day, twice a day, five minutes each time, for 2 to 4 weeks.

After that time, hoe off the weeds and grasslings with a sharp hoe; hoeing works best when the soil is dry. Don't dig or pull -- it only brings up more weed seeds. You can use Round-up but remember, you still have to hoe off the dead stuff.

Joe

If you remove the grass and weeds down to bare soil you will need to lay down some of that jute grid-like netting (that is especially made to hold things on slopes) before putting down the mulch or you'll have all the mulch at the bottom of the slope by end of summer.

If you were to mow the grass quite short before using the RoundUp wouldn't the short, now-dead grass actually help to hold the mulch in place? And the netting wouldn't be needed?

I would kill the grass with roundup. After it all looks dead, I'd water it and see if anything else comes up, then roundup that. After that, I'd put mulch down over the dead grass. The dead sod will do a pretty good job of holding water in place. After the mulch is in place, I'd expect a few weeds to appear, and I'd hit them with Roundup when they appear. As you said, I'd dig only where I want to plant something, and expect the normal amount of weeds to appear when you do, same as digging in the garden or anywhere else on your property.

I don't see any reason why you ever have to remove the grass, dead or alive. Even dead it will hold the soil in place, then simply rot away after a few years. I would expect more weed seedlings to appear on bare soil than in dead sod, and with bare soil you have potential erosion problems, so I think removing the grass will create more work and more problems than it solves. it certainly will be a lot easier to NOT remove the grass, and I think it will work better.

I removed all the grass with a hoe what a pain but I had 4" of thatch and large holes but it was insanity . Thought I was going to plant a water saving sort of lawn so I had to get out the thatch. But I'm going the the weed carpet with a rock garden. Home Depot has a long lasting weed carpet 25 years I think. So you could Roundup and after two weeks get up all the dead stuff. It took me three weeks of filling two city garbage cans full and were they heavy with the grass and the dirt is nice and flat. I have too many roses and other plants to use Roundup and chance the stuff getting into my gardens. Our mountain behind us is covered with blooming shrubs and trees which when the sprinkler goes off twice a week take care of themselves. I live in San Diego, PQ. My smaller hills have citrus trees, succulants, and herbs which really don't require much water.I gave up on veggies which I own lots of large pots but they just attract small animals which are destroying me but not as much as when I used fish emulsion and all the other highly recommended Hype. I did get Uncle Ians yesterday at Home Depot which has so far been keeping the rabbits,squirrels, and roof rats off my roses. Have fun !!!