There are many franchises, but my favourite is BBQ Chicken. Their crust is crispier than that of other franchises imo. It's one of the most well-known brands, so it should be pretty easy to spot anywhere, but If you need me to find one for you, let me know.
There are many different flavours, but my recommendation is to get banban (half-half) with fried chicken and yangnyeom. Yangnyeom is the original of all the flavoured ones, and that combo is the most loved one by Koreans. Highly recommend. The sauce is red, but it's not spicy at all.
If you want something new, Goobne Chicken is also a good option. They have oven-baked chicken, not fried chicken but it honestly is also very good. My favourite flavour is Honey Mellow, but please note that it's slightly sweet since it's coated with honey mustard.
As for chimaek (chicken and beer), pretty much every chicken place has beer, so just go for it. My favourite beer is Terra. Cass and Hite have a longer history, but they taste too bland for me. Terra is much more flavourful.