Ethereum on other chains

Hi guys,

I recently started learning about crypto and investing very little money in it. One of my obvious choices was ETH. I want to send it to a non-custodial wallet, but I have like 30USD in ETH and current gas price doesn't seem like a great deal for a small transaction like this. However I found out that I can send ETH to other chains like OKTC with way less fees. I tried sending ETH to my wallet on OKTC chain and I got ETHK in my wallet. I sent it back to OKX and I got ETH for it. So it works as it should, but I have one concern: if I undersatnd it correctly ETHK is techniacally not ETH, it is an other crypto that is always around the price of ETH. Is this a problem? Is it a good idea to keep my money in ETHK for years? Can it get inflated somehow or things like that?

An other chain I could use is Arbitrum and if I'm correct that is a layer 2 for ETH so could I get real ETH there? OKX says ETH-Arbitrum one, whereas with OKTC chain it said ETHK-OKTC. This seems good, but what confuses me is that Coinmarketcap doesn't show a contract for ETH on Arbitrom only on BNB, Solana and other chains.

So what should I do if I want to keep my ETH in the safest form possible?