Are all add-ons basically the same?

Please help me understand:
Are there actually big differences between add-ons used for searching for TV and Film?
e.g. do Umbrella and Seren do basically the same thing? (Particularly as I'd be using Real Debrid in both)

Are the differences basically to do with where they scrape for content and the lists they populate of Trending / Popular / Genre etc?
Are some better for searching certain types of content? For example if I'm looking for classic British comedy, would one be better than another?

If there *are* big differences in the results that different add-ons give you for less mainstream content, is there any way to do a power-search that polls several installed add-ons to give you more chances of finding what you're after?

Bonus question: are there differences between Real Debrid / All Debrid / Premiumize?? Would having more than one service be worth it when looking for rare stuff?