This month I plan on buying an M1 from the CMP; field grade.

I'm going to get an adjustable gas plug so the rifle will have an easier life. I see midway has two versions of these plugs. A two and a four port. So, what's the difference, really? Is there an advantage to one over the other? Oh, and I have a bayonet for it that I'm going to want to try at least once. Will either of these be compatible?

https://www.midwayusa.com/product/412046/schuster-dcm-adjustable-gas-plug-with-wrench-wwii-style-m1-garand-steel-parkerized

https://www.midwayusa.com/product/777146/schuster-dcm-adjustable-gas-plug-with-wrench-m1-garand-steel-parkerized

PS: Where's a good place to get those enblocs? I'd like to get a good handful of them and just keep 'em loaded up. I've only found them on ebay, midway, and brownells, the latter two are out of stock.

Been shooting garands for over 30 years the two best solutions regarding ammo are:
Start with some m2 ball or grand safe ammo from several different makers
Get reloading there are dozens of Garand safe loads out there and you can load 3 rounds for the cost of one factory. If you want to shoot your rifle a lot reloading ( or being rich) are the only ways to go

You don't need or even want either one if you plan on shooting M2 ball or reloads using IMR-4895 or H4895 powders.

46.0 grains of either powder is a generic safe load in M1 Garands when using Sierra, Nosler or Hornady 168 grain bullets seated around 3.250" to 3.300".

The Shuster plugs are designed to slow functioning (reduce the amount of gas that enters the gas cylinder). It's rarely needed in a standard rifle using standard ammo designed for it.

as far as I know, nothing. The two slot one is meant to mimic the aesthetic of the early solid gas plug and the 4 slot plug is mean to mimic the later gas plug meant for use with rifle grenades

I don't plan on shooting reloads as I don't reload nor do I have the space for it.

I'm planning on just buying some 30-06 in bulk from targetsportsusa and shooting that; something like this stuff, hence the gas plug.

https://www.targetsportsusa.com/prvi-partizan-30-06-springfield-ammo-150-gr-sp-pp341-p-97.aspx

EDIT: I thought I'd toss out there that I could absolutely get surplus M2 ball, but I'm choosing not to. I like to buy ammo that's available to me both online and in store for consistency's sake. Not only that, but I like to get my hands on ammo where it's availability isn't in question.

For example, I would have liked to have bought some surplus M193 for my ARs, but I can't always find that. I can, however, usually find Wolf Gold .223 so I bought that instead.

I've got a Schuster gas plug in one of my M1 Garands.

Works great.  No issues.  I only shoot my reloads (at this time) so I've never adjusted it since initial installation/set up.  I do plan, at some point (just never seem to get around to it) to reload and shoot ammo that would not be safe in an M1 with the standard GI gas plug, now I can do that when/if I get around to it.

I've never had to readjust it since that first range trip, so mine isn't working itself loose, or tighter, it's just staying where I adjusted it several years ago.

Gas plugs covered above.
AEC (new mfg milspec) clips available from SARCO for $1.50, $1.25 for 20:
AEC clips
These are the same ones CMP sold (and provided with the M1s); I don't see them on the CMP website now.

Just ordered 20 of those enblocs. Thanks for the link.