I'm English (although lived in Scotland for 25 years) and my DCs were born in Scotland so I thought I would give my appraisal of the difference between the two exam systems.
In Scotland, you start school 6 months later and you also finish school six months earlier so you receive a year less in education. You attend primary school from age 5 to age 12, then secondary school up to age 18. There are no sixth form colleges and you generally attend your nearest school.
In fourth year of secondary school at age 15, you take Nat 5 exams which are roughly GCSE level (or Nat 4 for the less able). Many schools only offer six subjects which is far fewer than the number of GCSE offered, however the pupils tend to be a year younger than their English counterparts. This means that pupils choose only four subjects, aside from maths and English which I feel is very early to specialise. They can, however, pick up subjects they have dropped in later years.
The next year is Higher year (fifth year) which is the most important year in Scotland. Able pupils will take five highers at once; and maths and English are almost compulsory. You then have a free choice of another three subjects. Highers are considered slightly harder than AS levels (in UCAS pts)
The gold standard for university entry in Scotland is 5As at higher (there are no A stars). Around 2500 pupils achieve this in a typical year. For popular courses, if a student achieves these grades, they are likely to receive an unconditional offer (many less popular courses have lower grade requirements).
Some students will go to university at this stage,but they would only be 16/17 years old so many stay on at school for another year (sixth year).
In sixth year, students can pick up subjects they have previously dropped and take extra Nat 5s, Highers or move on to advanced highers. Classes contain mixed ages so you could have fifteen year olds working alongside 18 year olds taking the same subject and exam level.
Advanced highers are the most difficult exams in schools in Scotland and an A grade in these attracts the same UCAS points as an A star at A level. Most students will take one or two advanced highers alongside extra Highers in subjects they dropped earlier on, but the most able can take up to four advanced highers.
If students then apply for uni in sixth year, they already have the achieved higher grades to enable them to apply to Scottish unis and receive any potential unconditional offers.
In summary, I think the Scottish exams are high stress due to three years of consecutive exams, but conversely the last year tends to be the least stressful if students have received a good selection of higher results in fifth year.
Many schools offer very limited advanced higher options: Highland schools may only offer six subjects at advanced higher level for example, so many students will just study highers as their top level.
Both my DC have gone on to study subjects which they haven't learn at school: law and computer science. Law is not taught in Scottish schools and our school has no computer science teacher.
Sorry this has gone on longer than I intended. 😊