Usually there is a foam gasket that compresses upon installation.
You can caulk all the way around, with immunity.
POLYSEAMSEAL is available in a small tube. You just need a narrow bead and it tools with your damp finger.

If you elect to caulk, use only 100% silicone and leave a small gap at the bottom to allow any trapped water to escape.

My preference is to buy some self adhesive foam weatherstripping and apply that to the back of the escutcheon plate in a horseshoe pattern. The thickness of the foam will be determined by the distance of the plate from the tiled surface.

You do not want double sided sticky foam as you want the plate to be removeable.

If you want to get a good seal with the convenience of easy repeated access, there is a simple way when using 100% RTV silicone sealant. Probably doable here but usually more suited to larger cooktops, sinks etc. in a kitchen or another counter area where later removal runs the risk of a strong but not completely accessible for severing silicone bond not smoothly letting go leading to something getting broken. It goes without saying that this hint should never be used for undermounts or anywhere else the original sealant's intact bead cured strength forms a necessary part of the overall design.

Silicone sealant bead has a useful property after it dries and is cut through, for example. New sealant applied to the two old sealant surfaces will act as a good gasket but will never form the tremendously strong bond of the original solid bead because the now new 100% silicone contacting old silicone surfaces can't dry underneath with the needed chemical action bonding like the all fresh original.
Thin black vinyl electrical tape stuck on one new sink (example) contact surface out of sight works the same way when it seals against the new 100% silicone sealant laid over the counter (example) contact surface. It may take a few weeks or months for the process to completely cure, but once it does, the device will usually easily release leaving the sealant intact and sealed to one side only as it separates from the tape.

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