I've been researching this more and still finding conflicting info! Very frustrating.

Here are some photos. It appears that the graft location my be part of the decision... the Tamukeyama is on the right and it looks like the graft is at about 24". The Crimson Queen on the left seems to be grafted at 12".

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I would ideally like to see about 2-3 feet more upward growth and a lot of lateral and weeping growth. Will I get that with these plants the way they have been grown??

I like the color and leaf of the Tamukeyama better, and I like that it is described as "more vigorous", which I take to mean that I will get to enjoy it larger, faster, than the other one... I will probably only live here another 4-5 years so that's important.

However, I have also read that the Tamukeyama is a more vertical, less lateral/weeping growth habit. True?

My idea was to plant it next to, and fairly close to (trunks ~5' apart) the dwarf white cedar you see in the photo. Thinking that they will sort of grow together and one will be a wispy blue-green vertical element, and the other will be a mounding, weeping, horizontal burgundy element. The cedar should get to be about 10' high x 5' wide. They'd be planted in the corner next to the front door:

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Do you think the Tamukeyama is OK there or would the CC be better? or is my plan just a bad one in general?

May as well plant what you think will do better long term. Either because:

A. ppl after you will think "boy the previous owner knew what they were doing" or "OMG, I'm tired of cutting down the previous owner's trees".

B. something will happen and you'll end up living there longer yourself or passing it on to family members.

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Far as which one to plant, I read Tamukeyama gets 5 to 7 feet tall in ten years. Probably is measured like Conifers.

Assuming this to be the case I don't understand how these nurseries don't list their expected maximum height also.

Imagine planting a cottonwood which says 30x20 only to find it grows to 100x50 afterwards!

Yeah... so that's part of the problem I am having. What size (and habit) can I REALLY expect from these two trees. Some descriptions of Tamukeyama, for example, list it as 15' with an upright, vase-shaped form. Some list it as 6-8' with a weeping form. How confusing is that?!?

I understand part of that may be due to culture (stake or no stake) so that's why I'm asking you folks here.... will either of these plants do what I want them to (eventually be ~6'-7' high and 8' wide)??? I am just brand new to japanese maples so don't know what to expect....

Mature size will depend entirely on graft location and how the plant is trained. Weeping forms that are trained to grow more upright - such as the two in your photos - will obviously achieve a greater height than those that are allowed to develop their weeping habit earlier (left unstaked after grafting).

Both tend to grow much wider than tall. Maple authorities (not just local nurseries) typically describe CQ as "mushroom shaped" and to 6-8' tall but upto twice as wide. Tamukeyama also mushroom shaped, 6-8' if staked or high grafted and again, twice as wide. Otherwise, there is very little difference in vigor, growth rate and foliage color.

Pick whichever one you like depending on current growth habit and graft height. Personally, I like these forms lower to the ground, so I'd remove any staking and let them start assuming a more natural, untrained form.

Please check my article about the pros and cons of Japanese Maple Tamukeyama and Crimson Queen