With the launch of its ad-supported tier, we get a new pricing structure for Netflix's plans. Starting with the cheapest and newest Basic With Ads plan, this goes for $5.99 per month with support for 720p resolution across your devices. Aside from getting ads, the content will be more limited than the ad-free tiers, and you can't download content for offline viewing. Then there's the Basic plan that's ad-free and costs $9.99 per month.
If you want 1080p resolution, you should opt for the Standard plan for $16.49. And then you can get the best resolution through the Premium plan, which supports 4K+HDR resolution for $20.99 per month. To switch accounts, head to Account in the top right corner. There's a Plan Details section there and the option to change plans.