Trading tokens on Solana has trained me to buy in smaller batches to increase the chances that my orders go through.

I do this when trading tokens on EVM L2s now, but not sure if it's necessary.

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nope, in general, tx work differently and there's little chance of it not going through

to protect from MeV, use cowswap and it usually goes through fine. Use twap on cowswap if it s a big one (never had the use for it myself).
You can check aggregators on defillama swap, those usually go through just fine too.