1password still on my iPhone after 1password 8 was installed, is it ok to just delete the old one?

I would strongly urge you to test 1Password8 before removing 1Password7 from your IOS device. Not sure it is easy to go back to 1pw7 once you've removed it.

The search functionality in general on 1Password8 has changed in such a way that with limited (i.e. small screen) estate to show information and select options/filters, for me it is terrible to find what I need. The AI suggestions are not intelligent enough to satisfy my needs and have to always go around the suggestions and dig deeper to find what I need. Ergo have to do more actions to get to where I need to be compared to 1pw7. Not only on IOS but also on my Mac.
When on the road and I need for example the PIN to my corporate credit card, it is only accessible with ease in 1pw7. Most likely because the information is stored in the "Credit Cards" type of record, which the AI does not find it important enough to show when I type the cards vendor name in the search box...

Of course I also use this comment to vent my feedback to the great developers of 1Password. I am a long time fan and will continue to be (for now). Having over 1500 items of all categories stored to search through, with the renewed search functionality, I do want to vent that you put a big dent in your imago/reputation for me.