You could use a 1000w heater, and it wouldn't be too much. Once the water reaches the temp you have it set for, the heater turns off. The higher wattage just means the heater will heat the water faster, or be able to maintain the desired temp if your ambient room temp is colder, and would only be harmful if a fish or invert were to hang out on or very near the heater while it's on. They're smart enough to move to cooler water if they get too hot, so not really an issue.
Tje only problem is if the heater ever stayed on (like the thermostat breaks), but that is increasingly rare. Dont worry. 2 200w heaters are fine, just monitor the temp everyday like with ANY heater to make sure they are keeping it where it needs to be
I have a 150 and a 200 in a 60 gallon. Same foot print just a few inches taller.
I like it because it keeps a nice even temp end to end. I have one in each corner.
One thing I recommend is to run it with one with the thermometer on the same side as the heater and make sure that side reaches your desired temp and do the same with the other. This kind of helps balance them. When I put the thermometer in the center of my tank my temp hardly fluctuates at all.
I use a 300w fluval in my 55 and a 150w Hagen in my 60.
Both tanks stay at their respective temps, the 150w just takes more time and probably ultimately more energy to run.
Also multiple or large heaters probably run longer since they are assumed to be used with more biger and thus more advanced setups. That and they don't need to run long and hard to keep the temp where it belongs.
A lot of people like the "Inkbird" heater controllers on Amazon.
You can plug in your 2x heaters to the controller.
I've got an Aqueon Pro 250w in our 75 gallon tank for the past 2+ years. I live in South Texas so it doesn't really get cold. When it does, house never gets below 68°. The 250w in a 75 gallon keeps up just fine in my experience.
If you want to keep an accurate measure and experiment, I found this great little glass thermometer that suction cups to the inside corner (or wherever you want to put it). Fantastic little thing, only like $8 USD