Although there are many different things about a keyboard that change the user experience, such as the switches (mechanical, membrane, or scissor; or different types of mechanical switches), the keycaps, and even the case. However, one of the most overlooked factors of customization for a keyboard is the layout. From wildly small to compacted versions of the classic full-size, these layouts are all an opportunity to save desk space, keeping only the keys you need. For anyone whose job requires a lot of typing, knowing keyboard layouts is as useful as knowing the alphabet. The right layout can help save you time, increase the longevity of your wrists, and more.
This is your standard keyboard layout. It has full function keys, F keys, arrows, numpad, and more. With many keyboards, there will also be multimedia keys above the numpad, or extra keys above the F row. These can include auto-opening the mail app, pulling up the calculator, or setting RGB effects. However, having such a wide keyboard, for most people, puts the arm holding their mouse at an unergonomic angle, and gives less space for the mousepad, for gamers.
The TKL layout is one of the most popular layouts. It saves tons of space on your desk, making your hand positions more ergonomic, but still has all the keys most people need. As machines take over many of the calculations that humans used to do, many people don't need a number pad anymore. In the TKL layout, there are usually no multimedia keys.
Among the keyboard enthusiast community, the 65% layout is quite popular. It has a very minimal size while keeping mostly the same dimensions for the alpha keys, but also has arrows and some extra function keys to help with productivity. However, it is sometimes hard to find the right sized keycaps for this layout as it is rather unconventional.
The 64 key layout is one of my personal favorites. It has tons of functionality, with all the essential keys (for me), plus the arrows and delete. Additionally, the case size is the same as a 60%, so if you are a keyboard modder, you can use 60% cases to mix and match, the only difference between a 60% and 64 key build being the plate and PCB. However, if you use right shift a lot, the 64 key layout might take some time to get used to.
60%, or compact
This layout is the most common for DIY keyboards, since it saves on material costs and is easier for small creators to design. It also includes all the keys I need, although you do not have the arrow keys.
This is a very controversial keyboard design where all the keys are lined up in linear columns instead of the normal staggered pattern. Ortholinear cultists will tell you that this layout is more ergonomic and more portable, while still keeping the same keys as a 60%. However, since the whole layout is shifted, it takes a long time to get used to this, and you will never really be able to use a laptop keyboard as effectively.
Overall, there are a ton of great keyboard layouts out there, and it is really up to you to decide which is best for you. Some notable layouts I did not include are 75% (65% but with F keys), 40% (the bottom 4 rows, but with the modifiers even more squished, and with arrow keys). For general use, many like the TKL layout as it eliminates the massive numpad, but keeps the arrows and some useful keys for general purpose use. Some like the 60% layout, as they have every key necessary for gaming, as well as most writing tasks. Again, it's totally up to you.