This is so true, to an extent. If your quarry is under 5 lbs no drag is required. Go after 150 lb and up and you not only need an excellent drag, the body itself must be capable to hold those forces.
Tarpon is the exception. 99.9% of fly fishing doesn't need disk drag like that. I've caught plenty of steelhead with a cheap clicker drag reel. There are plenty of more important things to spend money on: flys, waders, boots, bags/packs, nets, etc. All I need from a reel is to hold the line and to have enough drag resistance to no backlash when I hand-strip.
Fly reels are at the opposite end of the spectrum from baitcasting reels. THOSE are precision machines where quality matters and greatly impacts performance.
$400-ish isn't horrible but can't lie.. It would be great to be all-in at that price since I have no idea if I am going to love it or hate it. Still need a bunch of other stuff all of which are single purpose items.. other than the forceps which I remember using in a slightly different manner back in high school...
Four piece for a smaller package since I might backpack with it.
Rod weight.. I understand the numbers and matching weights. So...
Streams only for now. You narrowed down to 4 or 6. I would think lighter is better.
The rod/reel combo doesn't list a 4 available though.
All research confirms the line being critically important and probably disturbingly expensive.
$400 is PLENTY for a nice rod-reel-line setup for trout. You'd do fine with half of that.
The numbers depend on what size fly you're throwing, and isn't that sensitive (ie, 4 vs 6 isn't huge). 5/6 is typical for trout, start there.
WFF is all you need for most cases, and fits what fly fishing is good at. Most everything else is better accessed with casting rods and reserved for fly purists.
The fly line is the weight you through. The leader tapers from the thick fly line down to the thin line tied to the fly. The tippet is what you tie the fly to, just another word for leader in other fishing setups. None of this needs to be expensive.
You know what really matters most? Skill. So many new fly fishermen are like rich new jeepers that have no clue how to drive off road. You don't need to start with a $100k machine. Get something good enough to cover the basics and practice practice practice. If you want to spend money to jump-start your progress invest in lessons and guided trips, both of which often provide gear.
