For any kind of map functions, I would not attempt to use a Tablet to GM. I've found the full Roll20 browser experience on the majority of tablets (not full PC's slates but tablets like iPad and Android tablets) to be frustratingly annoying to use. However, using a tablet with the roll20 app for character sheet and complex macro rolling has been a god-send in many of my games. This is especially the case with anything having a complex roll action. Two-Weapon-FIghting Rogues with four attacks and 7d6 damage on each one... Swashbucklers that have a lot of AttackOfOpportunity interrupts that require rolls, just about any spell, applying buffs to a character sheet instead of keeping track of various +/- etc. As far as double-clicking and other mechanical techniques, that's going to be entirely reliant on the tablet and browser combo that you're using. ie: iPad vs Android vs. Surface, firefox vs safari vs chrome vs edge, etc, etc.
