I'm not a hard core rose-a-phile by any means, but I'll attempt to answer your questions: There are several classes of roses and I only have experience with Floribundas and Grandifloras, so someone more learned can expound on the rest.
TZ belongs to a class of roses called grandiflora. I don't know if Europeans use that classification or not, but they do here in the USA.
From what I know, and have read, Grandifloras usually grow taller and have larger blooms in clusters vs. one to a stem like Hybrid Teas...thus you get more flowers per stem. Some grandifloras can reach 7 to 8 feet tall.
PE (ET) is a floribunda which doesn't grow as tall and has smaller flowers, yet still in clusters. They typically max out at about 4' tall.
I only grow floribundas because my garden is very small and I only have about 60 roses as opposed to some members here who have hundreds.
Plus, growing floribundas gives me maybe 5 times the amount of flowers over a longer period of time. The ones I have also repeat bloom very well.
TZ is my only grandiflora and may indeed grow much taller in the next few years and that's fine.
Yes, both roses produce flowers on the top of the plant. Floribundas tend to produce a lot more side branches than HT's so you get more blooms, and from my experience they grow wider and produce more blooms. I've tried several Hybrid Teas over the years and have found them to be too much work for what they produced and are just too fussy.
I always tell people that for every rose that is successful in my garden there have been three before it that failed.
Where I live we have hot and humid summers. I'm basically at sea level and the Pacific Ocean is 1/8 mile from me.
Luckily, my soil is sandy clay and roses do fine in it. It's water retentive yet well draining at the same time.
Many roses I've tried do NOT like the heat and humidity of our summers. David Austin roses in particular...although I do have a few that tolerate the heat and humidity pretty well. Roses that thrive in the warmer interior valleys about 20 miles from here are abysmal failures for where I am.
From my experience, most floribundas seem to tolerate our damp coastal conditions as well as the summer heat and humidity and seem to be less disease prone. JUNE is a very overcast and damp month here, so rust and powdery mildew can be a problem if/when I don't spray with fungicide. Some years are worse than others.
Heavy clay soil can be a curse for some (if not all) roses. Try amending it with very coarse organic material that will allow it to drain. Mix it in liberally to about a foot or more. Your roses (or any other plants) will only grow as good as the soil they're planted in. Rose roots run deep, so if your soil is heavy compacted clay you'll need to amend the heck out of it so they can spread out as well as go as deep as they can. It's almost impossible to "over amend" heavy clay soil.
I've never grown roses on a slope or hillside. My garden is totally flat. It sounds like you need to construct some sort of water holding basins around yours (after you amend the soil) to prevent run off and then make sure they get plenty of water in your hot dry summers.
There's really no universal solution to successful rose growing in every situation. So many variables can affect how they grow and trial and error is the best way to learn. Patience is definitely required !
