iPhoto user asking about the latest Photos for Mac, iPad and iPhone

I can't speak re iOS Photos but the macOS Photos has every thing iPhoto had and more.

As for searching I always use Smart Albums. They have proven much more accurate than the text search field:

The new Photos has face and pet recognition. It also cauterizes photos that have cars, tables, window, chairs, etc,, etc., etc. The inanimate objects I search via the text search field.

I also create Keywords for each person of my immediate family, extended family and friends. When I add a photo with people in it I add the appropriate Keyword for each person. That way a smart album (Keyword is Jill) will show all photos quickly with Jill in them. If I want to see all photos with Jack and Jill I create a smart album as follows:

The new Photos has duplicate finder and can merge the duplicates. It also has these features:

However, you've waited so long you won't be able to use Photos to migrate your iPhoto library into a Photos library. It can only import the photos. You will lose considerable organizational effort, i.e. folders, etc.

However, the paid version of PowerPhotos can merge a iPhoto library into a Photos library with more of the organizational effort intact. A comparison of the two apps can be found in this user tip: Merging/Importing iPhoto/Photos library into Another Photos Library: PowerPhotos vs Photos

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If you're still using iPhoto that's been discontinued over 10 years now. With the devices you have currently you could have a Family Library in iCloud and on each device (except for maybe the 2015 iMac) where all devices would have access to the same photos in the library: How to use iCloud Shared Photo Library-Apple Support

Of course you will have to purchase enough iCloud storage to house your full sized library and expected growth. On devices with limited storage you can opt for Optimized storage which kicks in what the free storage hits about 10%. The local library will house an optimized version of the photo which will have to be downloaded in its full size for editing or use in any project or slideshow.

The iOS Photos app is much different than the macOS version and less capable IMO. I don't use it except to accept photos from family members and to transfer them down would my macOS Photos library. There will be a learning curve so it's best to start with a test library of a limited number of photos and experiment with that till you've got most of the capabilities learned.

I guess my answer to the question is that I don't know if the search has improved enough to satisfy you, but I've always found it adequate, and the cataloging feature with it's automatic classifications - a feature that requires internet access - seems, to me, to offer more opportunities. But you have an idiosyncratic form of classification and how that works for you will always be your limitation.

That said, you're moving to a new app - and you are as sooner or later your hardware will break and the replacements will no longer run iPhoto - and no matter what app you choose will require you to adapt your system to the features of the app. So I would start there. 60k is not a large library. How can you adapt your system to a newer application?

In any event, I would create a Photos library using maybe 5 thousand images and explore. See what you can do and if you like it or not. And if you don't, repeat the exercise with other apps until you find one that works for you.