With a very sharp blade in a mild razor, you should be able to achieve a reasonably close and irritation free shave. But getting a very close shave with it will take some learning and effort (lots of skin stretching, etc).
With an aggressive razor, you will no doubt achieve a very close shave, but at first you should expect some irritation until your technique improves. Getting an irritation free shave with an aggressive razor takes time to learn and a very slick soap.
You should definitely wait inbetween shaves for your skin to heal if you have any noticeable irritation.
This ^^^
A mild razor is more forgiving when learning. The shaves won't be (or may not be) as close as a more aggressive razor but will be more comfortable, and improve as your technique improves.
I prefer mild razors because I'm too lazy to work on my technique, so my shaves require three passes and touch up, and are never true BBS...close, but not 100% perfect.