Some people prefer to wait until a missed period as any lines that may appear on a test should be pretty visible/digital should be able to pick it up by that point. Testing earlier can show fainter lines (or negative digital) and leave you questioning whether it will develop, which can cause anxiety.
For me, personally, I've always tested before a missed period because I've always felt weird before my period was due to arrive.
1st pregnancy: tested 10DPO because I felt weird, and it was negative. Tested 11DPO because I woke up with terrible cramps but no AF and it was a very, very faint positive. I tested a few more times as I wanted to put positive tests in a box to surprise our mums with and noticed they weren't clearly visible. Sadly, the tests never got darker and I miscarried at 6 weeks.
2nd pregnancy: I felt tingling in my uterus and suddenly went off tea a few days later. Tested at 10DPO and had a very, very faint positive. I did test a few more times to make sure it wasn't the same story as last time because I was so afraid of not knowing it would happen in advance. My tests were very slow to develop and an early scan due to some pain showed I was measuring 10 days behind. I had a missed miscarriage at 9 weeks.
3rd pregnancy: hadn't been tracking as I was still recovering from my D&C, but suddenly kept having hot flushes and needing naps. I tested 9DPO and had a faint but clear positive. Healthy pregnancy with a little boy until 19 weeks when I went into spontaneous labour for no apparent reason.
4th (current) pregnancy: I had really strong implantation cramps at 7DPO. Woke up with milder cramps and unusual back ache at 9DPO. Checked my cervix, which was high and open, so I kind of knew. Tested and there was a faint but clear line. Line progression has been good thus far and I've been booked in for a viability scan by my consultant for 7 weeks.
So that's why some people like to test super early. If they've had a miscarriage, it can help prepare them for what's ahead. If they haven't, most people probably just wait for the missed period and then check with just one or two tests as the lines should be dark by then.
If your cycles are regular, and you know when you ovulated, you could get faint lines from 9DPO, but whether that would help you or make you more anxious than waiting it out, that would be for you to think about and decide. 12DPO, if you can be very certain of your ovulation date, should give a visible line if you're pregnant. Good luck!