I have tried a quite a few L1<->L2 across chain bridge - Hop, Connext, Li.fi, Orbiter, celer, etc, Across.to is one of the best.

The transfer fee is cheaper which consists 3 types of fees:

1. LP fees, which are set by the protocol
2. Slow relay fees, which are set by the user
3. Instant relay fees, also set by the user

The way that Across work is that it uses UMA’s Optimistic Oracle which acts as a dispute resolution layer. Across as a bridge, provides incentives to relayers to offer short-term loans to users on L1. These loads are repaid to the relayer within two hours from liquidity pools on L1. The pool is refreshed once fund from the L2 transfer settle. Because of these relayers, the transactions are fast. The speed of our transactions depends on the speed of these relayers.

Have a try my friends, this is definitely a well-established protocol.