I approach transplanting like this...if it's blooming, it's not ideal in the summer to transplant. BUT I have done it MANY times. I water them before moving them and have the hole ready before moving them and water them for two weeks after I move them. The blooms might die. They might not, but the plant will be fine! If it doesn't stay blooming, it will be fine next year. Well I guess I should clarify that if it was a weaker stemmed, taller perrenial, I probably wouldn't move it when it was blooming. They tend to droop and look unsightly when moved when blooming.
It's a very fast process if their root/soil ball are wet and the new hole is already dug. My problem is that I have to rely on Gabe for digging the holes. My shoulder hurts so much by digging them up, that I have nothing left to dig holes and vice versa if I dig the hole, my shoulder hurts too much to dig up a plant.
Like right now, when I wanted to dig up my sedum. They have buds on them and it's not a good time to do it, so I took cuttings instead. But I would have moved them anyway if I wasn't so eager to get it done without waiting on Gabe and I still might since my back garden isn't an ideal spot. My front garden would be much better.
I have spirea and it's pretty hardy. In fact some of it grew in my hosta planter. They are so hard to kill! I've pruned one until I thought it would die and it grows back every year. I don't know how big yours is, but mine was huge, so the problem is of course being certain you get enough of the root-ball. But what is nice with spirea is you can propagate it so easily. Obviously since a few clippings simply fell in my hosta pot nearby and grew. You can even root cuttings in a bucket of water. And if by chance you don't get the entire root-ball, it's ok. Spirea can be divided with a shovel, so at the worst, you'd have a smaller bush. If I remember I will take a photo of how much I pruned it down again this year. LOL It looks like a few twigs now and it will grow right back next year to being a bush. Oops forgot to mention, my spirea is not the pretty white bridal veil/reeves type. It's just the pink common gold mound/neon flash type.
I have euonymus, but it's the creeper type boxwood and not the bigger shrub and I have never tried to move them, but I do think they're very easy to move without issues. .Mine isn't the vine climber type. It's more of a ground-cover type. I would think nothing of just moving it because it takes so little care and thrives in my front garden. I have 3 of them.
Gooseberry I think would be better left for fall.
Iris I have moved in summer and early fall.
I have day lilies (SO MANY) and I hate them. I should take a photo of mine tomorrow, so you can see why I am not a fan. Too much of a good thing?! They were here when we bought our house and I sort of wish they were the yellow ones and not the orange. sigh I call them roadside-iums. I've never moved mine, but I don't think you can kill them. Personally, I would wait until they stop blooming.