bike wrench

Hey guys,

I'm looking to possibly upgrade the shifters on my 90s MTB from grip shifters to friction thumb shifters.

I'm currently eyeing the microSHIFT SL-M10 (https://www.microshift.com/models/sl-m10/), which is listed as being compatible with Shimano MTB 2/3×10.

Currently have a 7 cog cassette using an Alivio 7 speed derailleur. I also have a Deore LX M567 (8 speed) derailleur available, which would be a nice upgrade if compatible with the friction shifter.

Here are my questions:

1. Would that 10 speed shifter work with lower speed derailleurs?

2. What advantage, if any, would i get with a friction shifter listed for 8 or 9 speed derailleurs?

3. On the SLM10 shifter, it's got an indexed mode, too. Would that work with 7 speed, and if so, are limits set by the derailleur or do these things have hard stops built into them?

Thanks in advance.

UPDATE: I ended up spending a little (a lot...) more and getting a pair of Rivendell Silver2 shifters + thumbie mounts. Really nice quality and a beautiful ratcheting system. Loving friction shifters!