I prefer attending matches whenever possible to earn blue/green/red packs because it's my major sources to get these. But I also think that match result is not bad for matches I could not attend. So maybe we ought not to attend a match if we cannot concentrate, or just login in last minute to get the packs.
But for important matches, I prefer to attend and control the match on my hand. Honestly, I have some confidence on my in-match decisions.
I think the 4-5-1v is quite good formation for most teams as it is well balanced. It is easy to use. 3-2-3-2 is looked fine but I don't feel comfortable to use only 1 DC. Personally I prefer to use 4 defenders. It reflects that my team is defensive mind. Occasionally, I push up one defender and use 3 defenders. But at least 2 of them are DC.
4-5-1v and 4-4-2 are my preferred formation. But recently my team mainly use 4-5-1v or 4-3-1(AMR,AML)-1. With some multiple position players, my team can easily switch to many different formations e.g. 4-1-2-1-2, 4-5-1, 4-1-4-1, 4-4-1-1, etc so as to counter different opponents. I agree that the optimum formation is mainly dependent on players available. But I choose my players and build my team so that I can use my preferred formations.
I am not good at tactic and seldom make changes on these. I use mixed or both flank focus passing exactly the same way as you do. I rarely use offside trap (only temporarily use it during some matches). I usually use counter attack. I am not sure if these tactic are good, but at least I won some competitions (Yes, both my teams are league champion is last season) with these tactics.