Fps help

[SquidCompatriot]

(Gtx 750ti) Geforce experience has all of my settings on high 1080p as optimal.  I load in and run around my ship at an average 120-150fps.  However, when I join a mission, especially a public squad, my fps drops to 20-40.  Is there something I need to turn off? My AMD A8 3800 can handle my GPU just fine, and I can play graphics intensive games (ex: Dying Light) with other people no problem.

[BlooDONER]

Try to turn-off Nvidia Share (Shadowplay)

[Phasedragon]

Warframe is extremely CPU heavy. Your CPU is old and cheap even for it's time, so it's not going to handle warframe when it has to deal with an actual load. It's fine in your ship because there's nothing the CPU has to handle, leaving the GPU to run wild and handle the graphics just fine.

[LSG501]

Just done a pc reinstall and decided I'd go steam install this time... not the wisest thing I've ever done, steam caused me fps drops even with all the overlays turned off. 

Are you using steam or the standalone game?  Also I'd personally remove geforce experience from your pc as that can cause game lag too :)