You should only need an old school tv for light guns. Those use properties unique to CRT.
Genesis will play on LCDs enough to get started. But may not look very pretty. There's high end upgrade options like video processors to turn its RGB into forms US TVs understand.
TMSS isn't very important. It blocks a few of the earliest Genesis games. Also causes Genesis and 32X mode to display a startup screen (SMS or CD games don't show it).
CD attached can be useful. Enables music playback and more games. Model 2 CD unit is suggested for new users. Cheaper, more reliable, easier to fix... Just be aware of its wider footprint due to the drive's location.

