A bar bag would help balance the bike a bit (weight-wise).
Framebags I ride with most the time now as it can negate the need for a backpack, great for cafe lock/spares/multi tool/rain jacket/food/etc.
If you’re road based then, whilst new seat packs are great, ability to readily remove panniers is a benefit (harness seat pack systems ain’t cheap, and packing them takes practice/technique).
I’m sure you could find someone to borrow some off to trial if you wanted… if Scotroutes doesn’t have I’m sure he knows people who do 😉
Soft luggage requires frame protection as rubbing destroys paint.
I have a mix of Wildcat and Revelate stuff. I like the harness systems (bar and seat). I went ortlieb for a start but packing whilst luggage on the bike is awkward and removing and refining it a pain/fiddly.
A bar harness helps stand the bag off the bike and the rub is more or less restricted to the restraining straps.