Important is, that stray capacitance from signal contact to other contacts is very low. Otherwise there can be a medium to low ohmic path fom signal contact to ground, even if the contact is open. 5pF at 100MHz give an impedance of about 300Ohm!

I would use a Reed-relay. These are IP67, means are totally encapsulated with contacts resting in an inert gas chamber, have lowest on-resistance and highest reliability. Capacitance between open contacts is less than 1pF and capacitance to coil is about 2pF. Expensive types have massive gold contacts and can switch dry loads. There are good ones in SIL-package available.

Whether noise is coupled into signal chain via a relay, depends mainly on what potential the coil sits: Gets the coil a noisy voltage then noise can be injected into the signal path. So, the coil must see a noise free ground and the turn-on voltage should be filtered with a simple RC-filter. Then noise injection is normally no issue.

Kai