Do these vintage "aero" pedals require a cleat of some sort? It almost looks like there would be some sort of clip in nature to it for a cleat to engage, albeit I don't see the point of that when there's also standard clips and straps. Considering buying a pair of this style to upgrade from flat, unserviceable pedals.

Like most toe clip pedals, they'll hold best with a simple slotted cleat. However, they are commonly used without cleats.

I ended up moving to SPD clips as as I was having troubles with foot position and flexible soles when using walking shoes for longer rides.

If those are the true aero pedals, they take a non standard 1"diameter axle

Slotted cleats.

Pavarin 1 bolt slotted Cleats for Detto Pietro Shoes NOS NIP L'Eroica Italy | eBay

?, really?
those are not the earlier AX pedals

shimano after those brought out Dura Ace and 600 series "aero" pedals... barely a year before Look overturned the market with "clipless"

Yeah, slotted cleats. Those pedals weren't so much "aero" as low profile to minimize pedal scrapes.

Some Shimano pedals of this era used special slotted cleats that also interfaced with the tabs on the front of the pedal. Yours, these 6400 pedals below, and some 105s for sure. I don’t know if the cleats interchange between models.

pic thanks to bicyclists_retreat on ebay

Based on one reply here and the look of the pedal, is it safe to assume I would be okay to forgo the cleats and just use them as standard clip & strap pedals?

Absolutely. It was meant for slotted cleats but as was stated above, it also has a platform, toe clips and straps for riding fun.

I have found getting a decent quality thinner toe box shoe makes the difference.

Problem is the little wings on the front piece stick up. I think you can remove them and the clip is fine.

I've never owned the proper cleat for these pedals and I have used dozens of them with shoes.

Extra credit: the clips come in sizes. They should be marked, I find the medium and even large to be on the small side. The Dura Ace and 600 pedals came with metal clips. Lower models had a plastic/nylon clip that I often find cracked. Good metal clips are worth as much as the pedals themselves.

I'm a bit surprised than not that many prople used clipped, slotted cleat cycling shoes with their quill type pedals. I would think that using anything else could result in bad hot spots and pressure points because of the thin pedal cage against the bottoms of regular shoes.
People seem to be too worried about possibly not getting their feet off the pedals when they have to, but it's really easy to release the toe strap buckles with a quick flip of the wrist which becomes instinctive when stopping.
I remeber that it only took me one ride to get used to them.

I mentioned the flexible soles that became a bit of a problem with longer rides.

I seem to have misplaced my old cycling shoes, but I fear that my feet have grown in the last 30 years or so, so they may not fit properly.

Nonetheless, I always combine riding and walking, and found the old leather sole shoes without heels to be uncomfortable to walk in, and potentially dangerous on things like slippery stairs.

I'm not sure about shoes and the sculpted design of those pedals, although the typical cage pedals aren't fully flat.

Skate shoes have a very thick sole that should work well for this sort of thing. I reckon the sole on one of my pairs is about an inch thick and relatively hard. They feel quite nice for cycling just because they're stiff on the bottom like that. Not that it's optimal, but it's probably the best regular shoe type you can use.

I'll be riding with those at Eroica CA with LL clips for my size 12 1/2s. Still working out my "cleat" with shoe sole material and Shoo Goo.

On my pair with the single bearing you can remove the clips and put them on upside down on the opposite pedal therefore making a nice platform.

Be aware that these Shimano pedals require non-standard clips. Clips fatigue and break; I am not sure you can find a replacement for these when they go.

Younger riders would never have had to...! I loved my Sarroni, then my Lake cleated shoes (cannot believe I cannot find them anywhere). Nylon slotted cleats with zero float!

I replaced the earlier 105 (1050 series maybe?) with SPD-SLs but I remember that version was a nice platform. Still have them. The later ones had the metal clips and the little winged thingy.

As with most anything, you can find them on Ebay, sometimes at a decent price. It will take a long time for them to break. The Shimano 600EX and Dura Ace clips are identical. Size "LL" is extra large--these are harder to come by; Size "L" is just large. The size stamp is located on the bottom underside of the clip.

That piece acts sort of as a washer over the holes in the clip, which allow adjustment fore and aft. The screws holding the cleat are pan-head shaped, and probably should best be used with the piece, which is countersunk for them.

Mountain bike shoes without any cleats are pretty walkable and have relatively stiff soles.

Compared to quill pedals of the time they were most definitely "aero," with the Dura Ace version with blind end bearings probably being the most graceful clipped pedal design ever created.