Fairly simply inquiry. I was wondering how experience and levelling up would be balanced with both games.
because reaching level 50 early on would be no fun. And not terribly hard to do with access to both games.
I was also wondering if Broken Steel and the NV dlc had a cumulative effect on your character.
Meaning you would have the NV level cap of 30 + 20 from the NV dlc + another 10 from Broken Steel
50's the level cap still. however, there's plenty of ways of slowing down your progression, most notably the TTW_XPReduction optional file.
also, it's not simply "access to both games", the default start is in vault 101, and the train station in the CW is in the middle of the DC ruins, guarded by a bunch of SMs. which takes you to Doc Mitchell's to start NV, but the train station in Vegas is in Freeside. so it's not like you can just bounce there and back anytime you feel like it. well, after you've gotten both train stations on your map, you can bounce back and forth, but doing so at low levels will require skills or an interesting mod set.
To avoid leveling up too fast, TTW has an optional file (TTW_XPReduction.esp) which makes it so that at the beginning of the game one will level up at the same speed but with each level it will increase the XP necessary to level up and that increase will gradually get bigger the higher the level (so at the beginning leveling up seems normal, but after several levels it takes more XP to reach the next level, and after many levels it takes almost twice the XP to level up).
There are other ways to manage XP, for example Project Nevada has an option to choose the XP rate.
About the level cap, TTW uses the FNV game engine and level 50 is still the limit.
oh, did xpreduction get changed? last i saw it, it reduced xp gain as you leveled.
Before Jax released the XP plugin I released a series of plugins that cut XP gain by a set amount instead of dynamically adjusting the bump and base. Jax's version is far superior, but mine do still have a following. The one you're thinking of is probably one of the ones I released, based on the way you describe it.
My project Dash is on Kickstarter!
oh, nice. the bump and base method keeps me from getting sad about my xp gain
No mine also reduces XP gained for compatibility purposes. The mods that increase level XP reqs cause a huge level jump if they are disabled (because suddenly you have enough XP to hit 30, when the mod was saying it was only enough for 20)
Someone needs to keep me updated when they change plugins so I won't make a fool of myself 
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Practice Makes Perfect also works great with TTW, and slows leveling dramatically. At its default settings, however, it does increase the difficulty of the game somewhat, as you only level up the skills you actually use, instead of just dumping points into whatever you feel like.
