Frankly, I've never understood the allure behind the Smart Connector. Other than the ASK (which personally I dislike...prefer really keys to covered membrane), and one Logitech keyboard, what other accessories utilize this port?
I have an older Logitech Type+ Keyboard case for the original iPad Air which I quite like. Because it's bluetooth based, it actually worked with my 2017 iPad and will again with the 2018. (I sold the 2017 as I wanted Pencil support).
I'm trying to decide as well between the 10.5 and 2018 iPad.
And while I'd love to go Pro, the price differential (at least here in Canada) is more than double. Granted you get 64 vs 32gb.
Even if a new iPad Pro is unveiled in 2 weeks time at WWDC, I doubt the current 10.5 will drop very much. I've seen it discounted 15% on Apple's refurbished site. Even with that, it's still too much of a premium unless Truetone and speakers is that important. For casual use, I think the 2018 is the best deal...more so if you can find a sale on it (it's sometimes on sale for $299 at BB in the US).