Pace and GPS inaccuracy

No... Since the Forunner 620, all Garmin watch had cheap mediatek GPS Chips.

For pace you can use footpod (it can be Garmin or other firm) or Stryd which is now the best option.

i had the same weak gps problem since last updates. strange curves with i did not make are shown in the map. This is also a problem with strava segments.

I eventually gave up using my 5X for pace/distance, as it was so far out most of the time that it was counter-productive. I thought the Suunto Spartan Ultra was pretty bad, but actually looking back, it's miles better.

I would advise getting a Stryd footpod if you need accurate pace/distance. It isn't perfect, but it's as close as you'll get to perfect and is easily accurate enough to be a help and not a hindrance.

As others have said you need a footpod. I gave up on using my Fenix alone for intervals starting with the fenix 3.. It works OK for total distance and an ugly GPS track but forget trying to use it for short intervals. I use the garmin footpod but some will report back with mixed results. I've heard good things about the Stryd but haven't had the need to switch. I'm back into cycling primarily and use my Edge 820 so my Fenix is mostly used these days as a regular everyday watch. If I ever went back to full time running and depended on a watch to track metrics I'd switch back to a Forerunner 935

It's not the chip, it's the EXO antenna that causes this.
Best investment is a foot pod, not necessarily the Stryd but I agree, in regards with metrics we don't really have a choice: the FP is a must.

Let the track be wobbly and do what it likes; as long as the data is reliable it doesn't matter at all (plus it can be edited with third-party software and a bit of work for the precision maniacs like myself).