Digital therms are slaves to their software. Having three different manufacturers can complicate things for you. Understand that and you'll know what they are telling you. I've not heard of a way to tweak their accuracy other than doing the mental math after doing a boil test. Maverick says that a 3-4 degree temp difference on the boiling water test is acceptable error.
I have a cheap digital $10 quick read, two Mavericks (ET-732 and an older non-wireless single probe OT3-BBQ), plus I have the BBQ Guru DigiQ DX2. All give me different readings but it appears to be an algorithm issue more so than a mechanical response.
The cheap digital quick read gets used when oven cooking and it works fine for food temp. I've had it for heck, ten years. Never changed the battery. When it craps out I'll just buy a new one.
I use the OT3-BBQ in my gas grill, which doesn't get much use these days. I've had the OT3-BBQ for several years. I used all the fancy features, including alarms, initially. Went through a set of batteries in 3 months. I stopped using the fancy features, especially the alarms, and just use it for chamber temp. I haven't changed the batteries in at least three years.
I use both the Guru and the ET-732 together in my smoker. The sensitivity is greatest on the Maverick and I can see chamber temp change just from shadows on my smoker or the wind picking up. The Guru has much more of an averaging algorithm and I don't see it change much once it reaches the desired chamber temp. Both will eventually read the same chamber temp but the Maverick fluctuates more.
I don't use the food probe on the DigiQ DX2. It passed the boiling test just fine but it reads several degrees off from the ET-732. I trust the 732 for telling me the correct temp on the meat. The first time I used the DigiQ DX2 I used its food probe temp as a guide to see what I'd get. The ET-732 was telling me 140F on a beef roast. The DigiQ was saying 135F, my target temp. The ET-732 was correct based on the over-doneness of the meat.
I don't bother with any of the fancy features on any of the therms any more. All I want to know is chamber temp and food temp, and I know what to trust and how to use them.