No$PSX is a extremely capable no thrills PSX Emulator made by the talented developer behind several other emulators such as No$GBA. The core goal of No$PSX was to be able to work out of the box. This means there is no specific needs for a very particular version of Windows, no specially modified Video driver, no obscure and hard to find plugins, no requirement for virtual cd-roms, no requirement to have the PSX Bios to operate or require specific game setting tweaks to get games to run without any issues.
Emulation of the PSX Hardware is basically fully complete, with all features completed and working in some form, however there is always some edge cases that can be ran into so there may be some games that suffer from various issues still. A lot of work however has been done to try and ensure the core is as stable as possible.
No$PSX like some of the other top PSX emulators, emulates the BIOS via what is called a BIOS-clone. This has a few advantages, first of those is that it is free and legal, the PSX Bios itself is covered under copyright so your technically not allowed to download it. Secondly the cloned bios has the ability to be much faster then the original PSX bios, meaning No$PSX can run some games faster just thanks to an optimized clone. However there is one down side, there is a chance that compatibility may not be as good, this is mainly due to games that need to apply unknown patches to the clone bios. No$PSX tries to replicate them patches where possible but it can’t cover all of them.