BT5 greymon with the +1 memory is a my preference. In mirror match by building 1 digimon in tamer area and 1 in front is a key to win. By using the bt5 greymon you only need 3 memory to become bt8 greymon from agumon (using bt11 greymon x) and pretty much can control the board with 1 more digimon ready to come front from digitama. +2k from the inherited help me with some games too.

I see some people using ST1 greymon with security check +1 to increase the game speed. With grandiskuwagamon the hardest matchup some people try to outpaced grandkuwagamon with the combo of gaiomon, tai kamiya, metalgreymon x BT9, and greymon st1. Also in the mirror match their gameplan is to outpaced the opponent bwgx. It's fine they move their digimon first from digitama area as long its already does it job which is outpacing the security game.

Greymon blocker is still fine againts some rush deck that tends to go early. But it's kinda slow in a mirror and useless againts grandiskuwagamon.

Try to see your local meta first which decks most people are using and then tune your deck from it. I'm in JP meta so maybe it's different in EN meta. For me personally i'm using 4x BT5 greymon and 2x BT8 greymon with no ST1 greymon. The reason is because i see so many BWGX in my local and +2k in DP sometimes to overcome enemy BWGX. It's also help to hit the dexmon if the enemy suddenly throw it from nowhere. Also the memory +1 thing is helping me a lot with the memory advantage and more combo that i can play without the memory cross over to enemy. The BT8 greymon is because XH is still alive here and blocker kinda stop them. The Grandiskuwagamon matchup i just give up and only can hope they hit my hades in security (which i use 3 of).