Would this be terrible?

[Dineoutone]

If I singed an employment contract due to start in 2 months, and found a better job in the meantime and so had to tell job 1 I no longer wanted it....

Not strictly a relationship topic but I've always had such m good advice when posting here!

Well, maybe a bit of a pain for employer no. 1, but you have to do what's best for you. How will you feel in , say, 6 months time when you're doing job 1 instead of job 2 and wishing you were somewhere else. I say go for job 2 if it's really a better option, but tell job 1 as soon as possible to give them a chance to re-fill the role.

I'm worried any potential new place wouldn't want me if they found out...

It happens and no one will think you've done the wrong thing looking back - employer 1 will find someone else and move on - employer 2 will take it as a win and no one else will be that bothered. Do what's best for you!