The best option would be both together.
Opk’s will help you hopefully pick up your lh surge, but cannot confirm that you have actually ovulated seeing as it’s quite common to get a peak on an opk, and have a failed attempt at ovulation, meaning you’d body gears up to ovulate, then doesn’t.
So if you were solely going on opk’s you could easily assume you’re about to ovulate because of a peak reading, only to then fail, and your body reattempt later in the cycle.
Temps will confirm that ovulation has taken place as you will see a temp rise for 3 consecutive days.
I found the thought of having to wake up at the same time every day to consistently take my temp far too daunting, so after 12 months of ttc I invested in an OvuSense monitor. I wear it internally every night and it takes my core body temp reading every few minutes throughout the night then in the morning I connect it to my phone and it gives a reading that is even more accurate than regular bbt. I don’t have to worry about broken sleep, or sleeping with a window open etc affecting my temps as it’s all don’t internally over the course of the night. Not just based on one reading in the morning.
Temping can become obsessive though.
If you just want a general idea of when you might want to focus dtd then opk’s should be able to give you a decent enough picture. Just be warned as I said that it is possible to get multiple surges in a cycle. Not all women will though. I use opk’s too and it’s always correlated with my temps. But equally I know women who judging by opk’s would have been certain they ovulated, only for their temps to show that they haven’t.
Hope some of that helps!