Mostly RAM and how the operating system handles background apps, not picture quality. A Firestick, a Roku device, an Apple TV, and an Android TV box can all decode the same 4K stream at 15-25 Mbps without trouble, since that's a job for the TV's or box's chip, not the app. What varies is how each box behaves once a player app is holding a full channel list, an EPG (the on-screen program guide showing what's airing now and next), and a live stream open at the same time. Lower-RAM sticks show that strain first.

Not directly, but more RAM usually does. A base-tier stick with 1 to 1.5 GB of RAM can start to lag once a player app's channel list grows large, while a higher-tier box with 2 GB or more handles the same list without slowdown. This is a memory limit, not a picture-quality limit, which is why two boxes running the identical IPTV app and stream can perform differently even though both display 4K cleanly at 15-25 Mbps. The price difference between tiers is often just that extra RAM, not a better video chip, so check the spec sheet instead of the price tag alone before you buy.

Often, yes. TiviMate and IPTV Smarters are built to hold large channel lists in memory, and both let you hide unused channel groups, which reduces what the app has to keep loaded at once. Community discussion on r/TiviMate confirms this directly: hiding groups and running fewer active EPGs is what fixes slowdown on lower-RAM boxes, more reliably than switching to a different box entirely. The app's settings, not a hardware upgrade, are usually the first fix worth trying, and they cost nothing to test before you spend on new gear.

RAM first, storage second, and Wi-Fi capability third if you're not running Ethernet. Look for at least 2 GB of RAM if you plan to run a large channel list or multiple EPGs at once, since that's the specific bottleneck player apps hit. If the box only supports older Wi-Fi standards, a wired connection or a Wi-Fi 5/6 capable box matters more for 4K streaming at 15-25 Mbps than any other spec on the box. A cheap box with weak Wi-Fi will bottleneck a fast internet plan just as badly as a slow connection would.