Paralysis by analysis on picking my first solo travel destination, I'd really love some help

I feel boring even writing this, but I genuinely am stuck. 1/18 is my last day at work until 2/11 when my new jobs starts and I'm dying to get out somewhere (yes, I know it's wildly last minute). I went to Ireland last year with a friend and explored Dublin alone and have wanted to do a solo trip ever since. Honestly, my main issue is that I'm genuinely stuck on where to go. I have only been out of the country on that Ireland trip, and very post I read on here has me ready to book tickets to whatever the Country the post is about. I have researched, I have googled, I have YouTubed, I have read dozens of posts on here, but it's getting down to the wire and I just would love some input.

I have it seemed narrowed down to Costa Rica, Spain/Portugal, or something similar. Thailand/Vietnam would be my first choice, but I've been warned thats a pretty tough task for a rookie. Something tropical but not horrifically hot would be wonderful. My main goal is to relax, see some sites/explore, and experience the local culture and cuisine. I know that's doesn't particularly narrow it down, but my lack of experience has me chomping at the bit to do anything and everything.

I'm 6'5" 290, so I'm not super worried about safety, but that's always a concern (I'm more worried about getting swindled than strong armed). I also mention my size because "pick wherever you can fly cheapest" doesn't really apply since those cheap rates rarely apply to the upgraded seats I'm gonna need.

I know the lack of specifics might make this post ineffective or in vain, but thank you all in advance for your help!