It depends on what types of mods you have installed, and when they came out. Leveled lists used to be a reason, but many modern F:NV mods instead add entries to leveled lists via scripts on startup (thanks JIP!) and so are all compatible with each other.

I needed Bash for Cell edits primarily, because I wanted to use the old Interior Lighting Overhaul since I think it looks better than the newer scripted ones.

Wrye Flash is also great to combine patches into a single file to keep the load order down. Even with the mod limit remover, F:NV gets unstable if it has too many .esp's loaded. The patch combining feature is automatic and easy to use.

I did spend a huge amount of time creating a personal compatibility patch in xEdit. It's extremely simple to do manually once you learn it, but can take time. I had several overhauls like CCO and Vicious Wastes that I wanted to combine, with overlaps where I wanted to use the CCO version for some things and the VW for others, for example. I also had to do some manual edits to make sure I got the Brave New World faces and voices working with New Vegas Redesigned 3, the auto-patch missed some.