I've locally tried ollama with the models and sizes you mention on a MacBook with M3 Pro chip. It often hallucinated, used a lot of battery and increased the hardware temperature substantially as well. (Still, I'd argue I didn't put much time into configuring it, which could've solve the hallucinations)
Ideally, we should all have accesss to local, offline, private LLM usage, but hardware contraints are the biggest limiter right now.
FWIW, a controlled (running in hardware you own, local or not) agent with the aforementioned characteristics could be applied as a "proxy" that filters out or redacts specific parts of your data to avoid sharing information you don't want others to have.
Having said this, you wouldn't be able to integrate such system on a product like this unless you also make some sort of proxy gmail account serving as a computed, privacy controlled version of your original account.