Yappi
Go Buckeyes
No mics on the officials. So it probably was illegal formation. Just went by what the announcer said.1. You are correct. NFHS still differentiates between illegal substitution and illegal participation. A 15-yard penalty for IP in that situation is correct.
2. There is no such thing as “illegal procedure.” I’m assuming you mean illegal formation. Yes, live-ball fouls by both teams cancel and the down is replayed. The yardage of each foul is irrelevant. If the officials ruled the personal foul was a dead ball foul (they didn’t in your play), both fouls would be enforced.
Glad the officials got the calls right even though I disagree with those particular rules. Seems crazy that a technical issue can offset a player safety issue. We really thought the officials were deciding whether the player should be tossed out of the game because of the severity of the play.