Technically, there is no TNAP 2.0 as of yet for the slightly older Mio 4k that we all have. This one is specifically for the new Mio+.
It will run on our older Mio's, BUT, you won't have anything showing on the front panel LED screen. That's because the Mio+ doesn't use the same display. Also, for the Hauppage ATSC tuners, I believe it only works on the 955q so far (which I have). I have a copy of it from El Bandido that I'm testing now. As time permits, he is going to make a new firmware for our older Mio's.
Oh, and YES, you can have firmware's with different kernels in different slots, with no interference between them.
If you are using the OS Mio 4K as a receiver only and not interested in using newest plugins, there is no reason to update from the original TNAP to TNAP v.2.
As Primestar indicated, if you are using Haupagge 850 or 855Q ATSC tuners, these are not supported in the newer kernels and may not be supported in the future. I am currently working with Edision engineers to see if support for these discontinued tuners could be brought back for future TNAP releases.