I most often play with a combination of Oscuro's mod and Martigen Monster Mod. Oscuro's mod brings back a lot of the feel of Morrowind with its hand-placed loot and tighter control of leveling and scaling. It also provided lore=based reasons for enemies to be where they are, rather than merely plopping them down wherever they seem remotely plausible. I have always seen Oscuro's mod as much a roleplaying mod as anything else. This is what distinguishes it, in my mind, from the other overhauls.
I think Martigen complements this perfectly in that it adds a feeling of spontaneity and randomness to Oscuro's static placement of loot and enemies. With Martigen's mod running you never quite know what is going to happen, even if you reload the same save several times.
My main gripe with the way Bethesda handled leveling in Oblivion is with loot, not enemies. I'm actually pretty okay with enemies leveling and scaling with my character, as that provides a fair amount of consistent challenge as she gets stronger. It is Oblivion's heavy-handed, tone-deaf, obsessive use of loot leveling that I truly despise. So in some games I play with vanilla enemies and use http://www.nexusmods.com/oblivion/mods/3321/? by itself.
G's mod comes in scaled and unscaled versions. I always use the unscaled version in my games, as that is the one that does the most to stop Oblivion's horrid abuse abuse/overuse of item leveled lists and injects a bit of variety into what I find on enemies and in containers.