Hi OP.
I do not have personal experience of mood stabilisers because I am not bipolar. I was misdiagnosed as having a bipolar condition at one point, but that isn't really relevant as I was being medicated for a condition I did not have.
I do however have extensive experience of working with people with a Bipolar diagnosis, and also I socialise with them regularly as a consequence of meeting so many down the years. Everything I say to you is obviously anecdotal, and I am not in any way an authority on medications, but I will say that from my own observations and the discussions I have had with people who are prescribed the more traditional mood stabilisers such as Valproates, they do tend to 'work' to stabilise mood to a degree, but they often have a 'chemical cosh' effect and usually come with an array of unpleasant side-effects. Most people I know who have been on them long-term are dealing with the physical consequences of ingesting a toxic substance, associated lethargy, and are concerned to a varying degree about the ultimate impact on their long-term health.
The more atypical mood stabilisers can also come with side-effects, but they are not as toxic to the body as old-fashioned 'salts', and don't present the same risks to long-term health. I'd suggest you ask for a discussion about more of the atypical types and possibly try those for a period because they often are a case of trial and error and going through several before finding the one that 'works' for a specific individual. This is often the case when they are prescribed for other conditions as well, so it's a hallmark of these drugs rather than something specific to Bipolar conditions. Personally I would have gone through the whole gamut before I considered Valproates, and I was fortunate that at the time when I was misdiagnosed the psychiatrist in charge of medication also felt the same way and never entertained the idea of them.
Do you have any local Bipolar support groups or such? The ones I was involved with usually have a ton of insight into this sort of stuff and they are invariably open and welcoming to relatives with questions, even if the person with the diagnosis gets nothing from the group and has no wish to attend.