For MPEG encoding, you can get a PCI video capture card that will do mpeg encoding, there are some on newegg in the $40 area, but I can't attest to the quality of them, as I've never used them.
I can speak for the Ti4200. I've got that exact PNY card, a 64MB 8X AGP, and it's a really good card. I've played it with FarCry, HL2 and older games, and I have no complaints really. If it's a choice between a 4200 and an FX5200, I would go with the 4200. The 4200 is showing its age in newer games, but it is still a very powerful card if you don't want to enable AA/AF.
Also, The difference between the 64MB model and the 128MB model (aside from double the RAM), is that the 64MB model uses faster RAM. (3.8ns compared to 4ns, or something like that). The truth is, despite what PNY would have you believe, more RAM makes a bigger difference in performance than slightly faster RAM. I'd say you probably want to go with the 128MB model.
Hope this helps a little. you might decide gaming performance doesn't matter at all and get the 5200 anyway. You might also want to look at the lower end Radeon 9-series, the 9200, 9250, 9550, etc. I'm not sure how the performance of those stack up against the 4200, but they'll prolly be better than the 5200.