Lock frame rate to monitor refresh rate: Checking this box throttles the graphics rendering rate in each window to the physical refresh rate for the monitor where the window appears. By default (if this box isn't checked), the program renders graphics as quickly as possible. On a machine with a fast video card, this can render internal frames much more quickly than the monitor's physical refresh rate, which wastes system resources by rendering lots of extra frames that never make it to the physical display surface. This can place a high load on the CPU or GPU (video card), which can have unpleasant effects like making your GPU fan run constantly. Throttling to the monitor refresh rate will reduce the unnecessary extra work.
Stretch playfield image/video to fit window: If this box is checked, the playfield window will stretch its image or video to exactly fill the window, changing its aspect ratio (the proportion of its width to height) if necessary to make it fit exactly. Otherwise, the image is sized so that it fills as much of the window as possible while preserving its original proportions. The "stretch" option might look nicer if you have a computer monitor that doesn't use the common 16:9 aspect ratio, since it'll avoid blank spaces around the edges when displaying 16:9 source material.
Show "Dots" style high scores with fixed 4:1 aspect ratio in DMD video window: If this is checked, the "dots" style of generated high score graphics will be displayed with a fixed aspect ratio of 4:1. By default (if the box isn't checked), the generated "dots" displays are stretched to exactly fill the window. This only affects the video DMD window, obviously, not a physical DMD, and it only affects the automatically generated high score graphics, and only in the "dots" style. Normal media (images and videos loaded from files) are still stretched to fill the window as usual.
The fixed 4:1 aspect ratio option might be especially useful if you're exposing the full height of the DMD monitor, rather than masking it behind the more traditional WPC-era DMD cutout. The traditional DMD cutout is about 4:1, so with that, you'd normally set the DMD window size to about 4:1 anyway; it usually looks nicer in that case to exactly fill the window, in case it's slightly off from exactly 4:1. If you're exposing the full monitor height, though, stretching the "dots" graphics to fill the whole window distorts it considerably, so you might prefer to maintain the fixed 4:1 layout instead. This has the tradeoff that it'll leave some of the window area empty, but that's probably preferable to distorting the geometry beyond a certain point.
Enable videos: Check this box to enable video playback in the display windows (playfield, backglass, DMD, topper). Normally, video files are displayed whenever present, in preference to still graphics, since videos provide a visually richer presentation. Still graphics are normally only displayed when no video file is available. If you un-check this box, any video files will be ignored and still graphics will be presented instead.
You can use this option if video playback is places too much of a load on your system. Alternatively, you can simply delete video files or move them out of the media folders, but this option is obviously more convenient if you only want to disable videos temporarily.
Video/table audio volume: This lets you set a relative audio volume level playing back table videos and audio tracks. This setting adjusts the volume level globally, for all table videos and audio tracks. You can also adjust the volume levels for individual table videos on a per-game basis using the Adjust Audio Volume command in the Operator Menu, to compensate for particular video tracks that are much louder or softer than average.
Mute videos/table audio: Check this box to mute the audio playback for table videos and table audio tracks.
Mute button sound effects: Check this box to mute the sound effects for button presses in the user interface.
When a new game is selected, update all windows simultaneously: If this box is checked, PinballY will load new videos and images into all of the windows (playfield, backglass, etc) at the same time when you switch to a new game in the wheel UI. By default, the program instead staggers the loading, so that the windows are updated one at a time, rather than all at once. The staggered loading is designed to make the load process smoother, by spreading the work of loading the videos out over time. The trade-off is that you can see the windows refreshing one by one. If you don't like that appearance, you can check this box to tell PinballY to dispense with the delay and update all of the windows at the same time.
Crossfade time: This lets you change the duration of the crossfade effect that the program uses to transition between media when switching to a new game. The default is 120ms (about an eighth of a second).