Honestly, I agree the battery drain is a shock coming from a DSLR. Just be careful tho, as the R6 needs specific power levels for maximum burst rates. I usually stick with the Canon LP-E6NH Lithium-Ion Battery as my main since third-party ones can throttle your fps. For cards, the Sony TOUGH-G series SDXC UHS-II V90 128GB is my go-to for reliability. Also, look at the BlackRapid Sport Breathe Camera Strap to help distribute the weight better.

Agree on the batteries. Tbh, if you want a cheaper strap, SmallRig Camera Shoulder Strap with Quick Release is great. ProGrade Digital SDXC UHS-II V60 128GB Card handles 4K just fine... saves some cash.

Congrats on the R6! Since you are moving from a DSLR, you will notice the power draw is much higher due to the EVF refresh rate. Honestly, dont waste 80 bucks on the OEM Canon battery. I have been using the BM Premium LP-E6NH 2250mAh Li-ion Battery and it performs great for a fraction of the cost. Just make sure the third-party ones are specifically the NH version so you still get the max 12fps mechanical shutter speed. For memory, skip the overpriced brands. The Kingston Canvas React Plus 128GB SDXC UHS-II V90 is the best value right now. It hits 300MB/s read speeds which is plenty for 4K 60fps and high-speed bursts. For the strap, the kit one is garbage tbh. I suggest the Peak Design Slide Lite Camera Strap Black SLL-BK-3. Its way more comfortable and the quick-release anchors are a lifesaver when switching to a tripod.

Saw this thread earlier and just getting back to it. ^ This. Also, being a bit cautious with a new expensive toy is totally the way to go imo. It sounds like everyone agrees the R6 is a power hog and you really need those V90 cards to keep up with the buffer. I have been super satisfied sticking with the official gear just to be safe and avoid any weird errors. A few extras that have worked well for me:

• Delkin Devices 128GB Power UHS-II V90 SD Card for super fast write speeds
• Peak Design Clutch Camera Hand Strap which is great if you dont want a full neck strap
• Canon Battery Grip BG-R10 if you want to double your battery life and have a better grip for portraits Honestly, I am so happy I didnt go for the cheap knockoff batteries. Having that peace of mind when youre out shooting is worth the extra cash. Let me know if you need help setting up the autofocus later, it can be a bit overwhelming at first!

To add to the point above: I really have to disagree with using those cheaper third-party batteries! The R6 is such an amazing piece of tech, I just wouldnt risk it with anything other than a genuine Canon LP-E6NH Lithium-Ion Battery. I have seen way too many people deal with weird errors or swelling batteries after a few months... totally not worth the anxiety! Stick with Canon for the safety and the full frame rate. Quick tips for your setup:

• Get the Lexar Professional 2000x SDXC UHS-II 128GB Card since it is super reliable for those high speed bursts.
• Try the Think Tank Photo Camera Strap V2.0 Gray if you want something super grippy that wont slide off your shoulder. Its such a fun camera, you are gonna have a blast with it! Let me know if you need help with the settings.

^ This. Also, i am super cautious about my gear so I always go for extra protection right away. I am very satisfied with how these have been working on my R6 without any complaints.

• ULBTER Screen Protector for Canon R6 3-Pack
• SanDisk Extreme PRO SDXC UHS-II 128GB V90 300MB/s
• Peak Design Slide Camera Strap Midnight The screen protector is basically invisible and the SanDisk cards are worth the extra bit of cash for the peace of mind. Tbh I spent half my morning looking for a lost lens cap in the tall grass at the park today. I swear those things have legs and just walk away the second you put the camera down. I really need to stop getting distracted by every bird I see and actually pay attention to where I put my stuff... anyway, stick to the name brands for cards and you will be fine but yeah.

Late to the party but I had a similar struggle when I jumped from my old 5D Mark IV. Building on the earlier suggestion about the battery drain, it really is a different beast. I remember my first long wedding shoot with the R6... I thought two batteries would be plenty like the old days. I was sweating. Halfway through the ceremony, my last one was blinking red. I eventually rigged up a way to charge via a power bank in my pocket during breaks using a long cable. It looks a bit messy but basically saved my life more than once. For the strap, I actually went a bit rogue and DIYed a wrist loop out of some climbing paracord because I found even the fancy aftermarket ones too bulky for how I move. It isnt pretty, but it is secure. Honestly, the biggest thing I learned was just being ruthless with turning off the back screen when I wasnt using it. Small habits like that made a bigger difference for me than any specific piece of gear I bought, tbh.