There are TOO MANY things to explain. Therefore you need to build up the basic understanding first. In the process, you will start catching things when reading others writings online... It really is a process.
Ricky's audience is Canadians, hence he has very good "How To" type articles on Aeroplan. The best value to use Aeroplan, again, is NOT to fly Air Canada...
Chase and AMEX 還可以轉很多其他的航司 1:1 standard. Often with bonus to BA's family.
Aeroplan, BA IB Aer Lingus, (都是一家人但要求的裏數 尤其是 out of pocket Cash portion 大不同了去.）還有 SQ. These are the most valuable partners.
SQ business class can only be booked with either its own miles or Aeroplan's. SQ first class can only be booked with its own miles. You can check video reviews online to see how SQ F looks like... why it is so coveted..
I would suggest you to focus on a few programs that would fit with your travel pattern (how to travel) / meet your needs (where you usually go or want to go). Get the basics then build from that.
A huge advantage of mileage ticket is almost all are ONE-WAY structure - this adds incredible flexibility on building a trip. Before the Pandemic we often did round the world trip using One-Ways from multiple programs. The last one of RTW was in 2019, using Aeroplan's miles to structure the following trip:
MIA-VCE, VCE-IST-SIN-PER, PER-SIN-HKG, HKG-TPE-IAH-FLL. IIRC it was 155K miles per person. Used the allowed 2 Stopovers and an Openjaw, Destination was Perth. Stopover at Venice, Hong Kong. Openjaw was leaving from MIA, returning to FLL. Required overnight layover at Singapore, twice, and at Houston on return. Whole trip was in business class on TAP, Turkish, Singapore, Eva - but the last segment on UA was economy - anti-climax!
The actual trip went this way -
Miami to Venice, stayed 2 nights then took the Italian private train company Italo's modern train to Bologna for a couple days.
Took a Ryan flight to Bindisi, picked up an Avis for a week in Pulgia (the Heel on the Italian "Boot Shape" map).
Flew Ryan back to Bologna, stayed a night then dropped our bags at the hotel, took a train to Ravena to see its famous, increditble mosaic arts. Returned to Bologna for a night, took Italo again back to Venice for 1 night.
Venice to Istanbul to Singapore - an overnight layover. We spent a night at the airport hotel Crowne Plaza and took the time to tour the newly opened "Jewel" terminal, for the indoor fountain and garden with light shows... quite impressive.
Singapore to Perth, West Australia, the first few days stayed in town. Met an old friend (a German worked in US), he and I and a few others were invited by an American to form a tiny mileage focus group primarily to exchange info privately, back in 2006. We stay in private contact thru all these years. He happened to come to Perth to visit his old pals who were Qantas pilots, so a rare chance to meet in person again. He came to our hotel then we walked to Perth's tiny China town for a delicious dumpling lunch. We then took a pleasant stroll at in the neighborhood. He visited Perth several times so he could show us around. Later we walked back to our hotel and his train station. It is wonderful to meet again after the previous time in Hong Kong several years ago. I often meet my cyberfriends on trips when we happened to be in same location with overlapping time.
Then we picked up a Budget, drove south to explore the coastal area of West Australia.
Returned to Perth for a couple more nights then flew SQ to Hong Kong via Singapore - was planning to check out Gardens by the Bay at night but unfortunately it was raining on our arrival at SIN. Decided not to go and just headed to the hotel. I really want to see Gardens by the Bays at night. May be next year.
Spent a week in Hong Kong. Flew BR to Taipei, then its famous Royal Laurel Class to Houston. They handed out Jason Wu's PJs. Only EVA, Qatar and the old Alitalia airlines gave PJs in business class. 
Other airlines PJs are only available in F.
Other airlines PJs are only available in F.Overnight at the Houston airport Marriott which thank goodness had an M club open 24/7. (It was unmanned in late hours of the night). So we could have some drinks and snacks after midnight.
The next day at UA counter was a real customer service failure - Nobody wanted to check us in! The economy counter said even though you fly coach, the tickets were issued in F, go to the F counter. F counter said you fly coach on this segment, go to coach counter... All we wanted were to get BPs and to drop our bags since this was the last leg... So we headed to a UA counter set up in the middle from either end of the terminal, told the lady behind the counter that Nobody wanted to check us in. She took a look of our tickets, rolled her eyes, then proceeded to do the check in, even tied the "Priority" tags on our bags. Though it was useless as our bags came out almost the last at FLL!
Now you see WHY we dont fly United if we can help it!
In many cases, unusual Partner relationship can generate lucrative sweet spots - one of the most famous scenario is to use Virgin Atlantic points to redeem ANA business or first class. Much Much better value than using United Miles. One would never think about that Virgin and ANA are partners...
Read what Lucky wrote :
https://onemileatatime.com/guides/redeem-virgin-atlantic-points-ana/
