You can research them on the Appliances Forum. Figure out what you need and do some searching. I would also check on AJ Madison - my "go to" site when I need information about appliances. (They usually have pretty reasonable prices as well.) If you cannot find information on your choices, then post a question asking about them.

For example, if you have a 30" range/cooktop along the perimeter, look for one that's 36" wide x 24" deep with 650 to 900 cfms.

The reason for the 6" extra width of the hood is that when
smoke/grease/steam/fumes/odors rise, they spread out. You need to be
able to capture them into the hood. Since they spread, you need to have
extra width to accommodate the spread. If you have upper cabinets flanking your hood, you can sometimes get
away with a hood the same width - but it's not recommended. The upper cabinets help guide and corral the smoke/grease/steam/fumes/odors into the hood.

A hood against a wall should generally be:

• 6" wider than the cooking appliance (i.e., 30" range or cooktop / 36" hood; 36" cooktop or range / 42" hood).
• 24" deep
• 650 to 900 cfms
• Externally vented with a duct diameter at least 8" (10" is better and quieter)

If it's a hood over an island or perimeter (or any open space not against a wall):

• At least 6" wider than the cooking appliance
• 27" deep
• 900 or more cfms (you need more power when the smoke/grease/steam/fumes/odors are in the open where air currents are generally stronger than along the wall and will spread them out faster - so more width to increase the capture area and more power to "pull" them up.)
• Externally vented with a duct diameter at least 8" (10" is better and quieter)

In all cases, be sure to follow the manufacturer's instructions for installing - especially the height above the cooking surface. If you want to mount it higher, then you will need to oversize it - stronger cfms and wider hood.

Oh, and a remote blower will be quieter.

Be aware that hoods range greatly in cost, so consider your budget as well.