Can someone on this sub point me to info/resources? I’ve been a SMS owner/enthusiast for ~25 years but am not super knowledge

[/markiiisystem]

For example, two things of interest to me: 1) How many variants of the Master System were released in the US? I have four - 3x SMS (3010/A/B) and a SMS II that I AV modded that has…I think Alex Kidd built in, but I’ve also heard there was a SMS II with Sonic built in. What’s a good resource for info here? Are production/sales numbers available by the stamped model number?
2) My understanding of playing Japanese titles is limited, so please correct me if I’m wrong, but playing JP carts/cards on a US system can be problematic due to reasons (I’ve read header issues and pin issues, with hit or miss results using an adapter.) General advice seems to be get the MK-2000, but I like the appearance of the Mark III better. Apart from built-in FM, and I believe I’ve seen add-ons to add FM to the Mark III, do I gain anything going with the MK-2000?
For background, I bought my first Master System from a buddy’s dad my freshman or sophomore year of high school; it’s the 3010, with snail maze. A couple years later I picked up an untested one for $10, the 3010A, that happened to work. The SMS II, model MK-3006, fell into my lap via a local used game shop a few years back as “non-working;â€￾ a bit of soldering and an AV mod later it’s just fine. The 3010-B was obtained maybe two years ago, complete in box, and I bought it solely because it had a different model number than my other two.
Possibly of note - the “Aâ€￾ on my 3010-A looks stamped on after the fact, bigger and in a different font, but the “Bâ€￾ on my 3010-B is part of the label. I can try to link some pics if requested, of my consoles or other things in my collection, but nothing is super “of noteâ€￾ in it. I have a bunch of games, but nothing super rare and my Sonic is the PAL cartridge, and I have at least 3x guns and 5x each of both controller styles, but nothing special.
Again, apologies if I’ve posted any incorrect/misinterpreted info here; I’m very much a Sega fanatic, but hardware info beyond system specs with the Master System is a mystery to me. And, thank you in advance for any resources you can link to/information you can provide.

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