Tactics - Three at the back

Looking for guidance on using three at the back.

I was thinking

GK
BPD
BPD
BPD
DMC
MC
MC

Then get stuck, is it better to use Fullbacks as Wingbacks or 2 wingers as Inverted Wingback or even Inside Forwards?

Leaving 1 at the top

I typically play a 4-3-2-1 or 4-2-3-1 setup

Thoughts? Suggestions on which tactic to start off with?

I tried this setup last night and lost miserably. Could be due to the team not being familiar with tactic but switched back to a 4-2-3-1 and won both games handily.

I am using AC Milan with a strong midfield (Kessie, Bennacer, and Tonali and brought in Locatelli too)and decent Centerbacks (Romanagoli, Kjaer, Malenkovic and Varnier)

Wings are weaker with Brekalo and Politano with Isaak up front