Yes, you can apply for both JEE main and B.Arch. They would be conducted on different sessions, so it wouldn't a problem in attending both of the exams.
The exams would held from April 3 - 9 and the session timings would be 9:30 - 12:30 for paper -1 and 2:30 - 5:30 for paper -2.
Further guidelines can be found here:
IIT/JEE 2020 Online Preparation
Crack JEE 2020 with JEE Online Preparation Program, If you Do Not Qualify- Get 100% MONEY BACK