I didn't know what shifters I had but the paperwork in my bike folder it says I have SRAM TT. I am curious how the shifters impact the cassette size?
SRAM TT is bar end shifters for SRAM. For time trial, triathalon, and touring bikes. Not sure how SRAM handles compatibility between road and mountain shifters and derailleurs. Supposedly with Shimano, road and mountain shifters and derailleurs are not compatible sort of since 10 speed began. Not sure if SRAM allows mixing any and all speeds with any and all shifters and derailleurs.
Shifters effecting cassette size? No effect at all. If you have a 10 speed shifter of any kind, road or mountain or time trial, and the right rear derailleur, short or long cage depending on how big the cassette is, it will shift any cassette of any size, road or mountain, with 10 cogs. Staying with Shimano brand only. Or SRAM brand only. You can mix and match Shimano and SRAM chains and cassettes just fine. But for simplicity lets restrict to all Shimano or all SRAM. What has to be matched is shifter-derailleur-chain-cassette cogs. 9 speed SRAM shifter, 9 speed SRAM derailleur, 9 speed chain, 9 speed cassette cogs.