I have a 13 month Cavalier who's best friend is a Cavachon. They both have the most wonderful natures - friendly, polite, eager to please.
I researched thoroughly for my Cavalier and he was fully health tested. Look at the website cavalier.matters for really good research on questions to ask. They do have the risk of health problems - but I hope that by supporting breeding of fully health tested puppies this is a real way to try to at least to some degree breed out the health risks (which is the goal of the breeding protocol for Cavs). I think this is a breed worth saving. He does have food allergies (oh god the post chicken poop explosions until we worked that one out).
I would definitely recommend a Cavalier - for me he is the perfect dog - active but doesn't need too much exercise (although he does get every day about one hour off lead in the countryside and one hour noodling arounds the streets normally, but he would be okay without that every day) but still super enthusiastic (we're starting agility when he's old enough), SOOOO friendly and good natured - I am hoping for him to be an emotional therapy dog and its looking like he is going to be ideal for that - he really does bring joy wherever he goes. We were just at the vets for a little cut on his foot and the vet was all over him! BUT it is ESSENTIAL to make sure the full health test protocol is followed and also that it is not a puppy farm and a decent breeder.
As said, his bestie is a Cavachon and he is also a delight.
re the rescue/puppy debate - I got a puppy because I have never had a dog before and was concerned about how I would manage behavioural issues etc. This way I have been able to raise him from dot - so hopefully avoiding any major behavioural problems and also learning. I would probably get a rescue Cavalier next time. But I think the judgement for getting a puppy instead of a rescue is OTT - there are lots of reasons why people don't want to take a dog on with potential behavioural issues. (the obvious comeback is have all these people adopted children???)
And to be honest getting a puppy (i.e. v a rescue) is in no way the easy route - OH MY GOD - the time, the effort and the expense!! I went into it with my eyes open but it has been MUCH harder than I thought. But having said that I am really trying to do it right - and have learnt so much.
With these breeds it is really important to realise that they are very social. All dogs need company of course, but the most I leave mine alone for is 3 hours (dinner and a movie is now a planning nightmare...).
Many tears do have lots of older rescue Cavaliers who are just adorable - might def be worth thinking about and they will be able to help you identify if any behavioural issues that you might not be able to handle. Tbh though with a Cavalier this is unlikely (not impossible).
Good luck. I love my pup so much and he has brought so much more to my life than I imagined. And I think (hope) that he has a really good quality of life!