Beta testing is a social interaction, so has all the potential caveats. You want to trust whom you’re interacting with, but that shouldn’t stop you from reaching out to new players.
The more you do it, the more you learn whom and what to trust, and what you should take with a grain of salt. In general you don’t want feedback from just one person if possible and should not lay all your trust in any one person’s specific impression. The rule is if you get a specific subjective (non typo or bug) note from one person, that is an opinion worth considering. If you get that same note from multiple testers it probably is something important you may want to look at and consider changing.
The only major “strategy” I’ve employed against the “have as many people test as you can” rule specifically for IFComp is I try to only have non-voting testers. If I know Mathbrush isn’t entering the Comp, as valuable as his specific testing and feedback is, I would prefer his public review and vote on my game instead of knocking it out by having him test it. For newer entrants, this probably isn’t as easy and you should get as much feedback before release as you can.