SEO optimizing service pages

Haven't really found a good resource that talks about this. I'm working on a site that has 4 service pages. It's a very visual service so they have a lot of pictures and I think fairly nicely formatted text and around 800 words each. The pages have all the basic SEO stuff in place like meta tags, titles, alt tags etc.. The focus of these pages is conversions/lead generation, so the content is easy to digest and while optimized, not very extensive.

The site also has some blog articles between 1000-3000 words each for related keywords that are not too close to the keywords of the service pages for now.

My question is, what's the best practices for ranking the service pages higher? Should I keep adding blog articles for both less relevant and more closely related keywords and internally link to the service pages (and between the blog articles where it fits) or should I add more content to the service pages?

I'm afraid blog posts targeting more relevant keywords will outrank the service pages, since they have more content and I'm hesitant to bog down the service pages with too much stuff that isn't sale optimized so to say. For now they only have longer text in an FAQ section at the bottom. I guess I could write longer content at the bottom, after all the more converting content higher up but I don't know if that makes sense.

What's your thoughts on this? I would really appreciate to hear your take.