My fantasy football league has these positions:

Quarterback
Running Back 1
Running Back 2
Wide Receiver 1
Wide Receiver 2
Wide Receiver 3
Tight End
WRT 1 (Flex)
WRT 2 (Flex)
WRTQ (Super-Flex)
IDP (Defensive Player)
Kicker

Bench 1
Bench 2
Bench 3
Bench 4
Bench 5

After 7 weeks of play I'm 4-3, 4th out of 10 teams. Given my current experience this is how I compose my team.

You don't need extra IDP or Kicker since good ones are very common so easy to pick up a replacement in a pinch.

You want two starting Quarterbacks and at least one on your Bench who can score about 20 points, which seems to be about the average or a bit below average QB points output. On the other hand a QB getting 30 point is kind of elite performance day so I guess the way we have it there is not a lot of variance in QB scoring.

Four good Running Backs would be great since it's a fragile position with lots of injuries. Similarly two extra Wide Receivers in case of injury (less than for an RB) or bye week.

Definitely want two Tight Ends even though they don't tend to score as much except for the elite TEs. So that makes it:

Starters:

2 QB (QB and WRTQ)
2 RBs
3 WRs
1 TE
2 WRTs from the extra 5 extra players)

Bench: 1 QB, 3 players after WRT spots filled. The last spot should be whatever is best RB, WR, or TE out there.

So optimum team should have

3 QBs
4 RBs
5 WRs
2 TEs
1 RB/WR/TE (and I'd shade to RB because of high injuries)