Do you currently have gunnel mount rod holders? If you do, find out what diameter they are. More then likely if you do, they are from lee since that is who Grady has used for a long time, but that does not mean the outriggers need to be the same brand, just the same size. A 15' pole is what you want, not larger. For your needs and a boat that size that is your best bet without having a hardtop. There are many makes, taco, lee, rupp, they all make what you are looking for. If you plan to keep the outriggers up year round, keep in mind you will want a heavier pole that is more ridgid, some of the gunnel mount outriggers flex a lot, it all depends on what poles you buy. Oftern, ebay is a good spot to get new ones for a reasonable price, just make sure they are gunnel mounts and not t top mounts.
As for telescoping vs screw in, a screw in might be better, I've seen telescoping outriggers fold down underway when gunnel mounted, never a problem off a t top, but they do allow you to run with them stowed and then extend them on the grounds, to me more work...once your out there I want to fish, not spend 5 min untangling the lines and extending the outriggers personally, thast might not bother you if you do not plan to use them all the time. Lee and rupp make good outriggers, taco's are a little cheaper but aa good deal for the price typically. If you know what your looking for ie what size/brands and models that will make your search easier, but ebay might be your best bet if you want to save some money.