Michael Cox (excellent football analyst, very technical), did a good write-up for ESPNFC;
https://global.espn.com/soccer/english-premier-leag...
Loved this bit;
"Arsenal were always in control of this tactical battle: their early 3-4-2-1 caused Spurs' 4-3-1-2 problems down the flanks, forcing Mauricio Pochettino to re-shape in a 4-2-3-1. Then, when Arsenal moved to 3-4-1-2, Pochettino felt threatened by Arsenal's second striker, as he confirmed in his post-game press conference, and moved to a 3-4-1-2 of his own.
Later, Arsenal centre-back Shkodran Mustafi limped off injured and Arsenal didn't have a spare centre-back on the bench, so Matteo Guendouzi came on, and Arsenal went to 4-3-1-2. Both sides used three systems: this was the most tactical derby you'll ever witness. And Arsenal, usually the ideologues who play one way and one way only, came out on top. Tottenham, regarded as the Premier League's most flexible side, were outwitted."