2 accounts on one PC

no. but you can use another browser, or another user account for it. also, chrome has incognito option

first i would suggest not entering each others giveaways....this would be very suspicious....and
i also suggest to follow the rules here.....if you not follow the rules of activating and so on...this is even more suspicious...

I think it was recommended to warn support about it, to avoid risk of getting perma banned for multiple accounts.

Warn support. They answered quickly to my question about a similar topic though it was more related to the fact that I use SG at work and that I don't know if someone will use the site in the future (it's in a coworking, so, by definition, people are coming and going).