Most water filters won't remove heavy metals and fluoride. The ones thst might use reverse osmosis but that's an incredibly difficult and complicated process to get right and maintain- as you have to remineralise after it's been through the RO. Needs a lot of upkeep (salt for the saturator) and will likely cost a lot. It's possible to make your water quality worse by having it. If you live in the UK your water quality is really highly regulated - heavy metals are much more of a risk in bottled water. Only certain water companies dose fluoride, Severn Trent is one. But if you check your local water company website it will tell you if they do it. In terms of heavy metals, you can ask the water company to come and test your water - I had my home tested to check whether we had lead pipes. It's easy to do and also tests for other issues.
Water 2 by bear grylls is meant to be really good it removes 98.4% of fluoride and high percentages of other things like bacteria, parasites, chlorine, asbestos etc. I use bottled water for my LO, Evian and volvic have low sodium content and are safe for babies but it’s expensive so we’re thinking to invest in one too x
We have a Berkey and it's pretty good. Holds loads and not made of plastic. It's quite practical. And filters tons of stuff. You can check it out on their website or there is this vlogger lady called Farmhouse on Boone who has loads on it as well. It's a bit of an investment as first but in the long run it's not too bad