No. It is actually complicated. If both SIMs are on AT&T, Verizon, or T-Mobile then calls started from your Mac might use the iPhone to do the call (and at such point chances are the iPhone will decide which number to use), or it may use WiFi calling if that is setup and as far as I know you can register only one WiFi calling account on Mac and that is usually the number showing as the line you start FaceTime calls from. Check FaceTime preferences on Mac to know which of them is used.
Are you allowed to have two phone numbers on one Apple ID? Yes. There is no limit. Issue with Mac is that it doesn’t show the SIM/Line label so you can’t really tell which line is receiving the call. This is not an issue on Apple Watch but is an issue on iPad too I believe.