.arw is a Sony raw format, raw means it has larger file sizes and more ability to make drastic editing to the colors, highlights, and shadows. You can change the camera to shoot .jpg files which your Chromebook will readily recognize. You can also set it to shoot RAW+JPEG. If you want to simply extract or convert your existing .arw files to the more universal .jpg files, that is relatively easy.
As for a replacement computer, you should list a budget. A new $3000 Macbook Pro would be excellent, and has an SD reader built in, but I suspect that's not in your budget. There are many decent Windows laptops from manufacturers like Acer, HP, Dell, etc. in the $400-600 range.
As for an SD reader, most of them work just great, just pick any with a few thousand Amazon reviews and 4.5+ stars. If you're completely indecisive, just get this one: https://www.amazon.com/Anker-Portable-Reader-RS-MMC-Micro/dp/B006T9B6R2/
Here's the best Amazon price I see right now, $105 https://www.amazon.com/RG351P-Handheld-Console-Support-Classic/dp/B08TLZB3Y6/ref=pb_allspark_dp_sims_pao_desktop_session_based_13/144-1551942-4891656?pd_rd_w=svwfr&pf_rd_p=e896123b-6614-49c5-873e-d532e726c2f0&pf_rd_r=W8S4XQ11S2Q04HGF1DAN&pd_rd_r=81be8d54-4f9d-404d-8175-40b84b750074&pd_rd_wg=lqHnG&pd_rd_i=B08TLZB3Y6&psc=1
2 USB C Male to USB3 Female Adapter https://www.amazon.com/gp/product/B07CVX3516/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
for a card reader: https://www.amazon.com/gp/product/B006T9B6R2/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
A wireless adapter: https://www.amazon.com/gp/product/B00H28H8DU/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
For the last year I've used these with no issues, the first 2 were recommended by Russ from Retro Game Corps.
Plugable USB 2.0 Wireless N 802.11n 150 Mbps Nano WiFi Network Adapter (Realtek RTL8188EUS Chipset) https://www.amazon.com/gp/product/B00H28H8DU/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1
Anker 2-in-1 USB 3.0 SD Card Reader https://www.amazon.com/gp/product/B006T9B6R2/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
Syntech USB C to USB Adapter Pack of 2 USB C Male to USB3 Female Adapter https://www.amazon.com/gp/product/B07CVX3516/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1
I highly recommend a USB 3.0 microSD card reader if you have USB 3.0 ports (you'll thank me later after you transfer content from your old card lol). I bought this one by Anker: www.amazon.com/Anker-Portable-Reader-RS-MMC-Micro/dp/B006T9B6R2/ Worth noting that this model can also be used for 3DS hardmods, which is what I originally purchased it for.
Best of luck to you dude!
Should be fine, only thing worth noting is the USB2 vs USB3, the USB2 card reader will transfer files and flash images much slower.
It's not a big deal, I primarily use an Anker USB3 card reader now but for years I used a cheap Targus USB2 reader that came with a Nintendo DS flashcart I bought back in 2011 without issues. In fact, I still have the Targus one and it still works. It really doesn't matter, shouldn't be an issue.