If you've got an offer to go this year, I would just go this year tbh. We've got no idea when all the corona stuff is going to calm down, we don't know when there'll be a vaccine or how effective it'll be. There could be an even stricter lock down this time next year that means most people can't move to uni.
Idk about your uni and course, but mine is remaining largely the same, especially practical elements. I'm sure you'll still be able to go into see lecturers if you need to, and there should be SOME in-person teaching.
And as for freshers week, it is not worth taking a gap year (or 3 for that matter), which is likely to be pretty uneventful due to restrictions on travelling and most places aren't really hiring for workers or people looking for experience, for the sake of one week. I know a lot of freshers it to be incredible, and for many, it will be really fun, but there will be many more opportunities to have fun.