It will depend upon how well it is supported from below to prevent tipping. We have a compact basin in a unit that is fully supported from below and is stuck to the wall. I'd say pedestal types require securing mechanically.
Silicon might well 'do' but you won't know until you pull the basin hard enough to pull it off the wall and it lands on you or a child ... is there any reason for not bolting it to the wall? Why not just do the job properly?
Yes, do it properly with studs, and no silicone, other than to seal the top edge to the splashback once installed.
Apart from anything else, if the sink ever needs to me changed in the future, removing a sink stuck to a wall with silicone can be a nightmare. I speak from experience.
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