Are there considerable traffic jams in Paris?
I wouldn't like to waste most of my time in traffic jams. Is taxi a better option for a short term visit of Paris, like 3 days.
Does it make sense to rent a car when in Paris? Most probably, no.
Are there considerable traffic jams in Paris? Most definitely yes. Traffic in Paris has always been terrible, and the trend is to try to discourage people from driving, so there are reductions in the number of lanes, roads closed or with arbitrary one-ways which change every other crossing, and more. It can take an hour to drive a few miles.
Also, if you come from most of the US cities for instance, driving in Paris (like in many European cities) can be a nightmare, both in terms of orientation (don’t even try without an up-to-date navigation app) and the way people drive.
And even if/when you get to your destination, you have the issue of parking your car, which can be difficult and expensive.
Taxis can use bus lanes so it helps a bit, but in many situations they’re not quite the fastest option. Taking the metro is often the quickest option. But of course you will usually be more comfortable in a taxi than in a crowded rush-hour train.
Depending on your activities (business or tourism), itineraries, times of travel, weather, personal preferences and budget, the best options may be either a taxi, a “VTC” (Uber and the like — note however they can’t use bus lanes), public transport (metro, bus, RER, tramway, commuter trains), walking, cycling, using an electric scooter (“trottinette”)... It will almost never be using a dedicated car.
A good solution is to check your favourite map app before leaving to see the options. With a caveat: do not trust the RATP app when it tells you to take the bus. It is always waaaaaay too optimistic.