Better quality filters have excellent anti-reflection coatings ( very similar to or better than the lens anti-reflection coatings) preventing the kind of flare and distortion described above. Hoya calls the coating "HMC" ( Hoya Multi coating), while B+W, Heliopan, & Marumi use other nomenclature, but I find they work just as well, since I have them on different lenses.

Weight is a biggie in checked (50 lb max) luggage. I use a Benro carbon fiber travel angel tripod (15" folded)w/ small markins ballhead and similar carbon fiber monopod(14"folded) w/old Manfrotto monopod angle top, all with arca-swiss compatible quick releases, permitting quick on/off. I tried a walking stick with detachable head and 1/4x20 stud for holding camera, but it took too much time to attach. I DO use a cane, so the monopod was on a strap over my shoulder and utilized as needed. I have a small carabiner on my cane leash and just hook it to my pants belt loop when shooting. Hope this helps.
Stan

A lens hood ( rubber or plastic) designed for the lens you are using is essential to shield it from flare ( unanticipated light hitting hour lens from various sources- sun, cloluds, reflections-affects image in various ways), hood also is a 'bumpr' to protect lens if you inadvertantly bum,p into something or someone. Filters: my opinion is that dust, debris, spray, etc. will hit the filter and is easy to clean off with no possiblity of your cleaning scratching our delicate lens surface. Better UV filters with excellent front coatings transmit 99+% of the image photons and although they theoretically affect image quality the effect is only measurable on an optical bench using various monochromatic light sources, and is NOT visible on your image. Higher quality coated Hoya HMC, B+W, Marumi, Heliopan are all good. Unknown brands have unknown performance, but known brands ( previously mentioned) use the finest quality glass and coatings. Dealer profit is substantial on unknown brand filters, and their comments that they are" all the same" is not true, as you noted in the Polish (Dxo?) filter tests. I always us a hood and UV filter. I use lenses bought six months ago and 10 years ago.
Stan