Poco X3 Pro, or realme 8, Redmi 10 and Redmi Note 10 if prefer something lighter.
Watch more reviews, but it has to be among these brands.

Mi series still try to compete with other brands in camera, design and other features you normally expect in a flagship. Poco is performance-oriented, so it is willing to compromise on other areas, most commonly the camera is impacted. You have dig deeper to find what other areas are impacted. Redmi is the low-budget line for Mi, but Poco also makes low-budget phones.

Samsung M32 if you are okay to pay the "Samsung tax", but that model won't get the water resistance like other Samsung phones.

It's the additional price to pay when other brands can make phones with same spec and sell at lower price, charger included. To be honest, it isn't that obvious with this particular model when compared to the prices Samsung are charging for their flagships. On the M32 you are getting a combination of OLED with 90Hz, which you can't find on the other brands mentioned at this price. Take note that with OLED, comes Always-On Display too (except on iPhones). It's a big deal if their previous phone has Always-On and now they have to live without it. Not a big deal if they've been, let's say, using older iPhones that didn't have 90Hz nor Always-On Display.

They may or may not like One UI.

That said, if they are already used to 60Hz and LCD screens then just go for best performance. My previous phone had similar AnTuTu score (180k~220k) as these low-budget phones today and it was noticeably slow on some poorly optimized apps like Shopee.

A few more options with 5G support:
Poco M3 Pro 5G
Redmi Note 10 5G
Realme 8 5G

OLED is a type of display technology. It consists of millions of tiny LEDs. Every individual pixel can show different colour or turn off completely for the deepest black possible. This translates to infinite contrast, colours that "pop" and minimal blooming. LCD has a few LEDs behind the liquid crystals as backlight, hence it will shine some light even on a totally black image. OLED completely turn off pixels to show true black hence Always-On Display (aka Ambient Display) is possible with this type of panel, whereas in IPS LCD you are still consuming the same amount of energy to show black. AOD is a productivity and convenience feature so you don't have to touch your phone to check for time and notifications. You don't have to temporary blind yourself by waking your phone's screen in the middle of the night to see if you have new messages. The lack of multiple layers behind OLED panels also make it easy to make flip/fold phones.

90Hz means that the display is refreshing at a rate of 90 frames per second. Usually beyond 120Hz it is unnoticeable to human eyes. Below 90Hz, it is quite clear that the screen will feel less smooth. To some people, low refresh rate can cause dizziness when looking at the phone for too long.

AnTuTu is a combined performance score for CPU, GPU and RAM.

Can you even get Mi 10 at your RM1000 budget? I feel bad to have convinced you to raise your budget like that. Budget phones are cheap because they are missing one or two key features so you have to understand and accept those drawbacks. Most people can accept them hence why these phones are selling so well. If you know exactly the specs of the phones your parents are using right now, it helps your decision on which features you can cut and which you can't. You can just target those features their existing phones already have and try to maintain or improve them.