If I wear compression stockings only at night can it sill help my varicose veins? What are a good least cumbersome kind to wear?

Not really. At night I assume you are sleeping. The fact you would be in bed and not standing would negate the need for the compression as no gravity there.....you need the compressn hoosiery when standing to counteract gravity. Of course if you work at night and are not sleeping then that would be good time to wear them.
Just the opposite. Need to wear during day when you are up and active. Only need to wear knee highs and 15-20 mmHg compression to start Jobst / SigVarus are the best.
Stockings. The need for compression stocking is during daily activities. To get the best outcomes place the stocking on the legs prior to daly activities when you sleep there is no benefit to use stockings as your legs are elevated and closer to the level of the heart.