Is 280g your total tank setup volume?
Sump, frag tank?
I have total volume of about 240g.
125g show & about 115g in the basement. which dips to 60 in the winter
I have a 350w, 200w & another 200w
One in the sump, one in the fuge, one in the show tank
Any one heater can fail (shut off) & the tank will maintain temp
Any one heater can get stuck on, and the tank will not overheat
What is the room Temp where your tank will be located
2 smaller heaters are better then 1 big heater
3 are even better
My 350 is set highest, then one 200 right below that
The 3rd 200 below that
Most of the year my tank stays between 78-80
I use Titanium heaters, I use my older glass heaters for water changes