but you are right. I always hated Suran, mostly because of the layout but Balmora is a decently sized city. Had they gone more vertical with their buildings, they could've added a lot more NPCs too. But there's a reason why Balmora is a benchmark for vanilla modding 
If your frames survive that town, the rest of the game should run fine.I used to dread going to Vivec, got lost more than once there which was a good thing. Lore-wise it should've been even bigger but it definitely serves it purpose.
I've used Starfire's NPCs at some point, there were a couple other mods that added NPCs too and there was the LGNPC overhaul. I dropped all those with my last playthroughs though.
I never really played Oblivion, made several attempts but I can't get into it. Same thing with Skyrim, got a good deal of it's main quest done but when I couldn't kill the Blades I was like screw this, it's a waste of time, I might as well watch the 'endings' on YT. What I miss in those games is choice, I'm not out to kill anyone but I remember killing Vivec for the lulz with cheats and then that message appeared. I went DAAAAAMN and loved the game even more after that. The fact they let you play on when you finish Dagoth Ur was a brilliant touch too, they really should've done a DLC to expand on that.