1. For my use, do you recommend to use Trezor or Ledger. I know they both good but I just want to make sure. Is there any deal or coupons?
2. As I understood, when using a hard wallet, I won't have to worry about KYC. So in such situation, will you still recommend me to use the DAI coin? or the others that more trusted and reliable like USDC, PAX..
I suggested you use Ledger, but you need to observe by yourself. I don't know what coupons will be available so you can get a cheap price.
I recommend you to have USDT, USDC if you don't want to be afraid of the volatility, so you will see that your funds are not changed many times, but you won't have a chance to increase your fiat or bitcoin if you don't have altcoin because altcoin will have time to grow, but that is up to you.