Is it ok to paint old beams?

[CabinetKnob]

In an ideal world I wouldn’t, but the original purlin failed at some point and has since been supported with a secondary purlin. The whole thing sags noticeably and doesn’t look great plus I don’t like looking at it as it makes me feel like the house will fall down (despite structural report being ok). It’s also got paint on from previous owners and water staining. I'm planning to turn this space into a scandi/log cabin style snug and wondering about painting the purlins white to make them less noticeable and blend with the ceiling.

If yes, what type of paint should I use?

If it’s not a good idea, has anyone got any other suggestions on what I can do to make it less noticeable please?

I would try the Frenchic beam hack: https://frenchicpaint.co.uk/blogs/faqs/using-the-frenchic-beam-hack-on-other-areas-around-the-home

if you look online and on YouTube you will see what the final version will look like. I think it will keep your beams looking warm and natural which means you can change the paint around in future without having to worry about re painting the beams

What about a white wax, so some of the wood shows through.

I’d not just paint them no, what a shame that would be. And it won’t make it look better or hide it. The previous suggestions are good.