I'm 6'7" and have a variety of axes, in addition to technical ice tools. The axe I use most nowadays is a 66cm Grivel Airtech Evolution, with a slight bend in the upper shaft. Mine is the original style (2005?), yellow with no rubber grip at the bottom.
It's maybe just a bit short, but I have other longer axes too. If all
the terrain is going to be really easy angled glacier / snow terrain then at my height a longer axe might be OK, which is what they used to recommend for my height, probably up around 75-80cm. But the problem is when the angle increases and you are plunging the axe into the slope beside you, such a long axe becomes unwieldy and you have to lift your arm up higher each time to plunge it in and draw it out. Most worthwhile routes will have some such terrain (or steeper).
A longer axe is generally a bit unwieldy and more work on your wrist - I do have a 90cm axe and it's just ridiculous, I never use it. On the other hand I have an older Grivel AirTech Racing that is only about 60cm and it's clearly too short for me for general climbing. I have to bend over too far to use it, which affects my balance and makes for hard work. For many years I used a (UK) Mountain Technology axe of about 70cm and that was very good, but I find the shaft curve and more aggressive pick on the Grivel Evo means I can use it better on slightly steeper ground, maybe in conjunction with a second tool.
I climbed the bottom half of this route below (south face of Mt Epperly) with just a 75cm Petzl Snowalker axe, before using a second tool higher up.
But since then I've used the Grivel Evo. Last year I used it and a Petzl Aztarex hammer on the headwall on Ausangate, which is around 600ft of 50 degree alpine ice.
People might look at such routes and think you need two technical tools, but the variety of terrain on a big mountain means such tools are not the best option, much of the time.
A trekking pole(s) can often replace a long axe on very easy angled terrain, but you need to be careful and good on your feet, as if the terrain kicks up a bit and gets icy you've got no purchase for your hands. This is how accidents happen on some big mountains where most of the terrain is easy, but there's one short steeper icy bit that sees falls. The classic location is on the traverse above 17K camp on Denali, up to Denali Pass. Happens on Cho Oyu too. In such cases just one long-enough axe would have been safer.