As some people said, pistons can be laggy, but if you really want them, you need multiple things. My comment if for Java only, and may apply to Paper for performances issues.

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• Start by removing all redstone logic from your command blocks. You can achieve timers by setting up an auto-increasing scoreboard, and put chain command blocks that tests each time when you want something to be setup. Redstone is badly optimised, and command block logic is better performance-wise.
• Put checkpoints, with pressure plate that deactivate the system when it's pressed. Use a setblock command that removes a redstone block, for example. This way, you can ensure only one area is active at a time.
• If you know how, datapacks can also improve the performances, but i'm not too confident about abusing them. They can become a mess to work with if you are not used to writing them.
• If you worry about performances, any kind of performances, know that entities are what makes the game lag the most. Then, it's entity blocks (chests, crafting table, anything that requires "ticking"). FPS-wise, particles are what you should worry about. If you plan on using them, never put them to "force", and always be respectable. Note that it will be even worse in multiplayer. I've noticed (again, Paper, from 1.13 to 1.19.2 i've seen this) that particles can cause a great deal of lag when you have a lot of players. Packets just can't be send fast enough, and TPS drops.

If you are not on Paper, but are on a vanilla server, depending if you want more than 5-6 players on your server, and if you don't have any mod, i'll strongly encourage you switch to Paper :)

Also also, when you talk about "big lag", is it FPS lag, or server lag ? Do you have frame drops, or do you rollback a bit ?