I've used a Linhof Techno pretty much exclusively for six years, first with a roll film back and now also a Leaf Credo 60 and sliding back.
I have used only Rodenstock lenses (although was leant the SK60mm XL for a short time when I first bought the kit,) including the 90mm HR-W, 70mm HR-W and 55mm APO–SD.
The 90mm was awesome on both film and digital, but had a really bad tendency to flare and create a really hazy central part to the image if not using a hood, especially on overcast days. Using the hood, it was awesome across the field.
70mm HR-W is stunning, and even covers 6x7cm film with generous movements. This really surprised me considering its published IC and the hard disk, but there you go. I was pleasantly surprised!
55mm APO-SD is a great lens on film, and above average lens on digital. I think I have a pretty good copy, and use it almost exclusively with a centre filter. IMO, the filter is pretty much essential if doing pano stitches, which is what I use it mostly for. I only take it off when exposure times get really long, as without it noise it drastically increased after applying the LCC. (The SK 60mm was stunning and certainly better than my RS 55mm, but by how much I don't know. I couldn't see any difference on film.)
I think the Techno is an incredibly underrated camera; a wonderful tool and a joy to use. I love using the GG and have absolutely no problem focusing with it, except in very specific scenarios, like extremely dark environments or when focusing on flat surfaces like walls with minimal details to find focus on. In those scenarios though, if possible, I use some low tack masking tape and stick it to a surface, find focus on that, then remove it for the exposure. Not possible all the time, but works well for me 99% of the time I find myself struggling.
I'm sorry, but I've not used longer lenses on my Techno, but Anders Torger has written extensively on the subject. Maybe you have PM him and ask him to chime in here?
TJV