My load order. As you can see the only mods not merged with other mods are the ones I'm still working on.
[collapsed title=Load Order]
[X] FalloutNV.esm
[X] DeadMoney.esm
[X] HonestHearts.esm
[X] OldWorldBlues.esm
[X] LonesomeRoad.esm
[X] GunRunnersArsenal.esm
[X] Fallout3.esm
[X] Anchorage.esm
[X] ThePitt.esm
[X] BrokenSteel.esm
[X] PointLookout.esm
[X] Zeta.esm
[X] TaleOfTwoWastelands.esm
[X] TTWFixes.esm
[X] Ambient Temperature.esm < Needs work :/
[X] NevadaSkies.esm
[X] Project Nevada - Core.esm
[X] TTWHiresFramework.esm < Merged assets for all the Hires mods I use
[X] oHUD.esm < Will be redundant soon enough
[X] streetlights.esm
[X] TTWInteriors_Core.esm
[X] Mart's Mutant Mod.esm < Needs work :/
[X] TTWInteriorsProject_Combo.esm
[ ] Point Lookout Reborn by Jcro25.esm < Not finished
[ ] FO3 NPCs Travel.esm < Not finished
[X] TTW_Bobbleheads.esp
[X] TTW_MoreCookingItems.esp
[X] DarNifiedUINV.esp < TTW Edition with custom tweaks :D
[X] CASM.esp
[X] FPSWeaponWheel.esp
[X] HUD Extended - Ambient Temperature.esp
[X] Busworld.esp
[X] The Mod Configuration Menu.esp
[X] FlashlightNVSE.esp < Needs TTW-ified
[X] NeotropicsMedicalSystem1.12.esp < Removing soon
[X] NevadaSkies - TTW Edition.esp
[X] Merged.esp
[ ] outsidebets.esp < Will merge with NPCs Travel
[X] Overhaul.esp < PANZER
[/collapsed]
As for a limit - my goal is always to have the most non-conflicting, non bugged content possible in 15-20 plugins.