Are the following true - or pretty close to true? I'm not arguing any advantages or disadvantages, but am just curious as to whether my understanding is accurate (note when I say "virtually the same" I don't mean "exactly", but pretty darn close, no functional difference):

30-06 and .308: Same (.308 inch) bullet, virtually same amount power behind the bullet. Difference is that the .308 uses a "short" action casing - virtually the same capacity as the 30-06, but shorter and "fatter".

7mm and .270 - virtually the same diameter bullet. I think the .270 is .277 inch and 7 mm calulates into .276 inch (but I've seen it written that it's a .284 inch, and I don't understand how 7mm could give .284). Either way, virtually the same - they both round to .28 to the thousanths of an inch!

The .270 Winchester is a 30-06 casing necked down to the smaller .270 bullet - therefore, generally uses a lighter bullet with the same powder - it goes faster and flatter.

The 7mm-08 is "based" on the .308 case. Is this the same principle as the 30-06: .270 relationship? - an actual .308 size case necked down to a 7mm bullet? To me this would give the 7mm-08 very similar performance to the .270 Winchester - but I don't think that is true. The 7mm-08 doesn't seem to compete in terms of speed or trajectory with the .270, leading me to think it's a different casing than the .308 with less capacity??

Maybe the .308 casing is lower capacity than the 30-06 casing; therefore the 7-08 is a little less powerful than the .270?

Just musing and wasting time!