If you read the big text you just quoted you can see that a new OP code called OP_CHECKSIGADD is added to replace OP_CHECKMULTISIG(VERIFY) working with Schnorr signatures.
Apart from that the behavior of OP_CHECKSIG is also changed if it is inside a Taproot script as it needs a different sighash and treats signatures as Schnorr signatures not ECDSA.
There are also some small changes such as OP_(NOT)IF mandate "minimal if" (the item popped by the operation has to be empty array or 1).