I recently finished my 8.5", 1:8 "pistol" build with a Sig brace.

I'm hoping to pick up a suppressor but don't have a timeline for that yet.

Usage will be plinking, possibly an occasional hog hunt and maybe duty as a home defense weapon.

I have 1k brass but need to get the rest of the components to reload.

Will I miss out on much if I load only subsonic rounds for it? I know the brass will last longer, but other than that I don't have any experience with the round.

Its your gun shoot what you want through it . just be aware if you want to use the gun for home defense expanding or fracturing sub-sonic bullets will get expensive fast .  Barnes black tips are the holy grail for the 300 fired super-sonic but canget very expensive also . I dont plink with them I just use them for hunting . I have had good luck with nosler 110 grain varmageddons as a general purpose round . They are accurate in all three of my guns , accurate and work good on varmints and so far have performed well on deer out to about 130 yds . A big plus is you can buy 100 noslers for the price of 50 barnes . Also I think the noslers would work well for home defense since I think at those ranges there would be less chance of over penetration due to the bullet construction.
hope this helps.

pulled 147 FMJ.......17 grains of W296 or H110...........inexpensive and I shoot it all day long..........my paper punching round........But, with that being said........shoot what your wallet allows.........I got a friend who refuses to shoot 55fmj from his AR's...........he always shoots the 62 grainers.............

I cast 130 gr out of wheel weights, powdercoated.  ~1400 fps.

Speer 125 TNT bullets are cheap and shoot good. My favorite is over some 4227. They run around $100 per 500.

Since I handload, I don't really care about the cost for my hunting or defensive rounds.

What I'm hoping for is to have some cheap plinking rounds the same weight as the hunting/defensive rounds so I can keep everything basically the same with minor tweaks.

Is there any benefit to shooting supersonic from the .300BLK on a day-to-day basis?

Supersonic does have a flatter trajectory than subsonic, and the bullets are cheaper, so without a can for the time being I'd say focus on supersonic loads.  You can always run milder loads to help take it easy on brass.

From what I'm reading, the subsonics (except for VERY expensive bullets) are ice picks... so they'd be worthless for hunting/defense anyways...

Supersonic is cheaper to plink with because you dont need $0.40 heavy bullets and can get by with pulled 147s or whatever you can find. (Lead bullets may be more affordable for subs).  Supersonic are also probably going to be cleaner with less unburnt powder up in your receiver.  They're also easier to get to cycle the action and lockback on an empty mag without a supressor, and supersonic powders are a bit easier to find.  Subs are also not that much quieter without a can.  The uncorking noise is still pretty damn loud on a short barrel 17" from your face.

I shoot 125sst and 208amax but if I was trying to save some coin Id definitely go with the 147 gr pulled bullets. Plenty of loads out there that would suit you just fine.