Best adjustable heater?

I know there’s probably not any one answer, but I was stupid got a preset heater by accident. I then got an adjustable hygger(?) but it just wasn’t working as it was intended to and I opted to rely on the preset one instead because it was just getting too warm otherwise. Still not ideal. I’ve got a 20gal long for my betta and I’d rather have the temp at 80 but it’s not even a consistent 78 (like I’m pretty sure it hits 77 because I’m struggling to find a thermometer that actually works and the three I’ve tried have all been Not Right as well).

My other betta has one of the topfin sets and his heater has been doing real well by him so far, but reviews have been making things harder for me to make a new choice with confidence.