shopify-packer VS themekit

Shopify Packer written by Eric Hayes is probably the best thing happened to Shopify theme development since Shopify stopped supporting Slate. It's everything we all hoped for and that's a promise. Packer uses Webpack 5 with zero config to compile, bundle, split and minify your modern development technologies and start a server for development with hot module reloading actually working perfectly. It can also create, list and manipulate (delete, download, deploy etc) themes from your shop which is a lifesaver sometimes. I also love using Eric's Shopify Packer because it uses SCSS, Stylelint, ESLint, Babel and PostCSS. It can analyze bundles and have multiple entry points for templates and layouts. It's actually a CLI tool that’s installed globally and you can start a new project or integrate Packer with an existing theme in ridiculously little time. Most importantly you can easily customize all settings for the site and webpack if needed. Eric also provides quick support for the packer so i would highly recommend it and also buy him a beer because he deserves one for this!

Themekit - development tools to interact with the Shopify platform to watch for local changes and upload them automatically to Shopify

Look into Shopify Themekit (https://shopify.dev/tools/theme-kit) After setting it up you can easily clone into your existing Theme and edit it freely. You can even set up hot reloads and see your edit in realtime on your store.

You have a TON of freedom on the storefront. The checkout, as mentioned before, is pretty darn limited. However you can "monkeypatch" the checkout flow and make most things happen. As far as Liquid goes, read the docs to suss out the limitations and capabilities. I'd recommend using either Themekit, Motifmate, or standard Liquid package locally (won't include Shopify-focused features but will have templating, basic utils, etc) to have a workflow where you can use source control, have local development, and a smooth deployment process.