Upgrading from DSLR to EOS R1: Use lens adapter or buy all new lenses?

[twoegrets]

Long time reader, first time poster.   

I'm a long time EF lens owner, 400 2.8, 300 2.8, 200-400 (560 with built in), 500 f4, etc...  I own 2 x 1dx mark iii's as well and that has been my go to body for the past 3-5 years.   I've spent many years shooting mostly sports and concerts.    Sharpness is a must for me.   ....and I've been incredibly happy with the sharpness I get currently.   

All that said, I'm ready to go mirrorless, but not yet ready for an R1 + 40k in new lenses.    I've been reading and reading about the R1, very intrigued, sounds like a great body, and I'm considering making the jump with the $150 lens converter.    It just seems way too easy?    I'm really in love with my EF lenses.    I know the R1 is not out yet, but does anyone have history with the R5 mark ii and large EF lenses with the converter?    Some lenses fair better than others Im sure?   If the glass is great it's great and should be a smooth transition?    Is my disbelief that a $150 converter can make a $6500 R1/$7500 EF lens combo work seamless together a misplaced fear?   Maybe it's tough for me to believe that a $150 converter can make 2 expensive pieces of camera gear work seemlessly?

I'll eventually upgrade lenses, but it will be a process for me.   How frustrated will I be in the meantime?

Hope I'm making some sense.    I'd love to hear anyone's experiences.    Thank you!

[twoegrets]

Thanks everyone for all the thoughtful replies.   I'll share a bit more.   The 1DX Mark iii is prefect for sports and  90% perfect for concerts, the noise level is an issue for me and has been for a while.    I shoot everything from hard rock concerts to the symphony.    The symphony, comedians, spoken word, politicians, etc...    That's where the problem got started.    Even in silent mode the 1dX 3 is way too **bleep** loud.   It's the 20 comedians or celebrities each year that I have issues with - when the audience is super quiet.   I also shoot in the same venue 75 times a year so I don't have the luxury of not caring about the noise or the patrons as I'll be back in the same place in 3-5 days shooting something else (and want to keep my job).

I can be shooting a Sebastian Maniscalco or Jim Gaffigan and when I only get 5 minutes of shooting and I have to wait for the 3 big laughs to land on the crowd in order to have them make noise and then blow off 75 fast frames while a dozen old people are giving me dirty looks for the "cannon" (pun intended) that I'm firing off at the stage standing 5 feet away from them.  That's where the problem lies.    I never really knew how loud the 1dx iii was till I shot an acoustic artist in a theater with a dead silent crowd.     I'm shooting with the 200-560 or the 400 most times with a monopod.     Any Sports I shoot - noise is never an issue obviously.     

I've waited for a while to buy a mirrorless, pondering it for a few years and about ready.    I like the R5 ii and the larger files but I think the R1 will be more comfortable and closer to what I'm used to with my current 1dx iii.

[ebiggs1]

"Not have to worry about mirror lock-up?

Hmmm, on the top one thousand things to worry about, that is number 999.