The problem being electrum does not have USDT acceptance, while besides this BTCPayserver accepts connection of Cobo valult, Coldcard, Wasabi, Specter desktop, and Passport not sure if any of these wallets are similiar to electrum which runs on your laptop but can accept USDT deposits??
Although some of the wallets you mentioned do support USDT, you won't be able to use that with BTCPayServer. You can only connect your bitcoin wallet.
I also saw another thread about omniwallet & coinomi but not sure if they support automated checkout with verification if coins recieved and mark order as completed once it verifies on wordpress website? Also not sure if they have any intermidiary charges and centralization as the other services I described earlier?
They don't. Omniwallet and Coinomi are wallets and not payment processors.
I suggest you check Coinbase Commerce. It has a WooCommerce plugin[1], they have a self-managed solution, and accept BTC as well as stablecoins but the fee is a bit high compared to what you found (1%).
[1]
https://www.coinbase.com/commerce/integrations/woocommerce